Piezoelectric material, piezoelectric element, and electronic device

ABSTRACT

There is provided a piezoelectric material not containing any lead component, having stable piezoelectric characteristics in an operating temperature range, a high mechanical quality factor, and satisfactory piezoelectric characteristics. The piezoelectric material according to the present invention includes a main component containing a perovskite-type metal oxide that can be expressed using the following general formula (1), and subcomponents containing Mn, Li, and Bi. When the metal oxide is 100 parts by weight, the content of Mn on a metal basis is not less than 0.04 parts by weight and is not greater than 0.36 parts by weight, content α of Li on a metal basis is equal to or less than 0.0012 parts by weight (including 0 parts by weight), and content ρ of Bi on a metal basis is not less than 0.042 parts by weight and is not greater than 0.850 parts by weight 
       (Ba 1-x Ca x ) a (Ti 1-y-z Zr y Sn z )O 3   (1)
 
     (in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric material, morespecifically, to a piezoelectric material that does not contain any leadcomponent. Further, the present invention relates to a piezoelectricelement, a multilayered piezoelectric element, a liquid discharge head,a liquid discharge apparatus, an ultrasonic motor, an optical device, avibrating apparatus, a dust removing apparatus, an imaging apparatus,and an electronic device, in which the piezoelectric material isemployed.

2. Description of the Related Art

Lead zirconate titanate is a representative lead-containingpiezoelectric material, which can be used in various piezoelectricdevices, such as an actuator, an oscillator, a sensor, and a filter.However, a lead component is harmful to the ecological system becausethere is a possibility that the lead component of a wasted piezoelectricmaterial may dissolve into the soil. Accordingly, research anddevelopment enthusiastically performed recently is directed to non-leadpiezoelectric materials that can realize non-lead piezoelectric devices.

When a piezoelectric element is employed in a home electrical applianceor a similar product, it is required that the piezoelectric performancesdo not greatly change in an operating temperature range of the product.If a parameter relating to the piezoelectric performances, e.g., anelectromechanical coupling factor, a dielectric constant, a Young'smodulus, a piezoelectric constant, a mechanical quality factor, or aresonance frequency, greatly changes (for example, by an amountequivalent to 30% or more) depending on the temperature, it becomesdifficult to obtain stable element performances in the operatingtemperature range. In a phase transition of the piezoelectric materialaccording to the temperature, the piezoelectricity is maximized at aphase transition temperature. Therefore, the phase transition is afactor that causes a great change in piezoelectric characteristics.Therefore, it is a key to obtain a product whose piezoelectricperformances do not change so greatly in the operating temperature rangethat the phase transition temperature of a piezoelectric material is notin the operating temperature range.

When a resonance device (e.g., an ultrasonic motor) includes apiezoelectric composition, the mechanical quality factor that representsthe sharpness of resonance is required to be large. If the mechanicalquality factor is low, an amount of electric power required to operate apiezoelectric element becomes higher and a driving control of thepiezoelectric element becomes difficult due to heat generation. This isthe reason why a piezoelectric material possessing a higher mechanicalquality factor is required.

A non-lead piezoelectric material expressed by a pseudo-binary systemsolid solution of{[(Ba_(1-x1)M1_(x1))((Ti_(1-x)Zr_(x))_(1-y1)N1_(y1))O₃]-δ%[(Ba_(1-y)Ca_(y))_(1-x2)M2_(x2))(Ti_(1-y2)N2_(y2))O₃]}, in which M1, N1,M2, and N2 are additive chemical elements, is discussed in JapanesePatent Application Laid-Open No. 2009-215111.(Ba_(1-x1)M1_(x1))((Ti_(1-x)Zr_(x))_(1-y1)N1_(y1))O₃ is a rhombohedraland (Ba_(1-y)Ca_(y))_(1-x2)M2_(x2)) (Ti_(1-y2)N2_(y2))O₃ is atetragonal. Dissolving two components different in the crystal systemenables to adjust the temperature at which the phase transition occursbetween the rhombohedral and the tetragonal around the room temperature.For example, according to the discussed contents, the phase transitionof BaTi_(0.8)Zr_(0.2)O₃-50% Ba_(0.7)Ca_(0.3)TiO₃ occurs around the roomtemperature and a piezoelectric constant d₃₃ at 20° C. is 584 pC/N. Onthe other hand, a piezoelectric constant d₃₃ at 70° C. of the samematerial is 368 pC/N. More specifically, if an increased amount in thetemperature is 50° C., a reduction amount in the piezoelectric constantd₃₃ is 37%. The above-mentioned piezoelectric material is characterizedin that a phase transition at which the piezoelectricity is maximizedoccurs around the room temperature. Therefore, although theabove-mentioned piezoelectric material demonstrates excellentpiezoelectric performances around the room temperature, it is notdesired that the piezoelectric performances is remarkably variabledepending on the temperature. In the above-mentioned material, the Zramount (x) is set to be greater than 0.1 to obtain a rhombohedral of(Ba_(1-x1)M1_(x1)) ((Ti_(1-x)Zr_(x))_(1-y1)N1_(y1))O₃, which is an edgecomponent.

The material discussed in Karaki, 15th US-Japan Seminar on Dielectricand Piezoelectric Ceramics Extended Abstract, p. 40 to 41 is a non-leadpiezoelectric ceramics that can be obtained by sintering BaTiO₃ thatincludes additives of MnO (0.03 parts by weight (parts by weight)) andLiBiO₂ (0 to 0.3 parts by weight) according to a two-step sinteringmethod. The addition of LiBiO₂ substantially increases the coercivefield of BaTiO₃ including the additive of MnO (0.03 parts by weight)linearly in proportion to the addition amount of LiBiO₂. Further, theaddition of LiBiO₂ substantially decreases the piezoelectric constantd₃₃, the dielectric constant, and the dielectric tangent. When theaddition amount of LiBiO₂ is 0.17 parts by weight, the piezoelectricconstant d₃₃ is 243 pC/N and the coercive field is 0.3 kV/mm. When theaddition amount of LiBiO₂ is 0.3 parts by weight, the coercive field is0.5 kV/mm. However, according to an evaluation result, theabove-mentioned piezoelectric material is not desired in that thetemperature at which a phase transition occurs between the tetragonaland the orthorhombic is in a range from 5° C. to −20° C. Further, theabove-mentioned piezoelectric material is not desired in that themechanical quality factor at the room temperature is low (less than500).

The above-mentioned conventional non-lead piezoelectric ceramics is notdesired in that the piezoelectric performances greatly vary in theoperating temperature range of a piezoelectric element and themechanical quality factor is small.

To solve the above-mentioned problems, the present invention is directedto a piezoelectric material that does not contain any lead component andis characterized in that the temperature dependency in the piezoelectricconstant is small in the operating temperature range, the density ishigh, the mechanical quality factor is high, and the piezoelectricconstant is satisfactory. Further, the present invention is directed toa piezoelectric element, a multilayered piezoelectric element, a liquiddischarge head, a liquid discharge apparatus, an ultrasonic motor, anoptical device, a vibrating apparatus, a dust removing apparatus, animaging apparatus, and an electronic device, in which the piezoelectricmaterial is employed.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a piezoelectricmaterial includes a main component containing a perovskite-type metaloxide that can be expressed using the following general formula (1), afirst subcomponent containing Mn, a second subcomponent containing Li,and a third subcomponent containing Bi, wherein the content of Mn on ametal basis is not less than 0.04 parts by weight and is not greaterthan 0.36 parts by weight when the metal oxide is 100 parts by weight,content α of Li on a metal basis is equal to or less than 0.0012 partsby weight (including 0 parts by weight) when the metal oxide is 100parts by weight, and content β of Bi on a metal basis is not less than0.042 parts by weight and is not greater than 0.850 parts by weight whenthe metal oxide is 100 parts by weight

(Ba_(1-x)Ca_(x))_(a)(Ti_(1-y-z)Zr_(y)Sn_(z))O₃  (1)

(in the formula (1), 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and0.986≦a≦1.02).

According to another aspect of the present invention, a piezoelectricelement is characterized by a first electrode, a piezoelectric materialportion, and a second electrode, wherein a piezoelectric material thatconstitutes the piezoelectric material portion is the above-mentionedpiezoelectric material.

According to yet another aspect of the present invention, a multilayeredpiezoelectric element is characterized by a plurality of piezoelectricmaterial layers and a plurality of electrode layers including at leastone internal electrode that are alternately multilayered, wherein thepiezoelectric material layer is the above-mentioned piezoelectricmaterial.

According to yet another aspect of the present invention, a liquiddischarge head is characterized by a liquid chamber that is equippedwith a vibrating unit in which the above-mentioned piezoelectric elementor the above-mentioned multilayered piezoelectric element is disposedand a discharge port that communicates with the liquid chamber.

According to yet another aspect of the present invention, a liquiddischarge apparatus is characterized by a portion on which an imagetransferred medium is placed and the above-mentioned liquid dischargehead.

According to yet another aspect of the present invention, an ultrasonicmotor is characterized by a vibrating body in which the above-mentionedpiezoelectric element or the above-mentioned multilayered piezoelectricelement is disposed and a moving body that contacts the vibrating body.

An optical device according to the present invention is characterized bya driving unit that includes the above-mentioned ultrasonic motor.

According to yet another aspect of the present invention, a vibratingapparatus is characterized by a vibrating body in which theabove-mentioned piezoelectric element or the above-mentionedmultilayered piezoelectric element is disposed on a vibration plate.

According to yet another aspect of the present invention, a dustremoving apparatus is characterized by a vibrating unit in which theabove-mentioned vibrating apparatus is provided.

According to yet another aspect of the present invention, an imagingapparatus according is characterized by the above-mentioned dustremoving apparatus and an image sensor unit, wherein a vibration plateof the dust removing apparatus is provided on a light-receiving surfaceof the image sensor unit.

According to yet another aspect of the present invention, an electronicdevice according to the present invention is characterized by apiezoelectric acoustic device in which the above-mentioned piezoelectricelement or the above-mentioned multilayered piezoelectric element isdisposed.

Further features of the present invention will become apparent from thefollowing description of examples with reference to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a configuration of a piezoelectricelement according to an example of the present invention.

FIGS. 2A and 2B are cross-sectional views schematically illustratingexample configurations of a multilayered piezoelectric element accordingto an example of the present invention.

FIGS. 3A and 3B schematically illustrate a configuration of a liquiddischarge head according to an example of the present invention.

FIG. 4 schematically illustrates a liquid discharge apparatus accordingto an example of the present invention.

FIG. 5 schematically illustrates the liquid discharge apparatusaccording to an example of the present invention.

FIGS. 6A and 6B schematically illustrate a configuration of anultrasonic motor according to an example of the present invention.

FIGS. 7A and 7B schematically illustrate an optical device according toan example of the present invention.

FIG. 8 schematically illustrates the optical device according to anexample of the present invention.

FIGS. 9A and 9B schematically illustrate a dust removing apparatus, asan example of a vibrating apparatus according to an example of thepresent invention.

FIGS. 10A, 10B, and 10C schematically illustrate a configuration of apiezoelectric element that can be incorporated in the dust removingapparatus according to an example of the present invention.

FIGS. 11A and 11B are schematic diagrams illustrating a principle ofvibrations occurring in the dust removing apparatus according to anexample of the present invention.

FIG. 12 schematically illustrates an imaging apparatus according to anexample of the present invention.

FIG. 13 schematically illustrates the imaging apparatus according to anexample of the present invention.

FIG. 14 schematically illustrates an electronic device according to anexample of the present invention.

FIGS. 15A, 15B, 15C, and 15D are graphs illustrating characteristics ofpiezoelectric materials in comparative examples 2 to 5 and in examples15, 17, 18, and with respect to temperature dependency in relativedielectric constant.

FIGS. 16A, 16B, 16C, and 16D are graphs illustrating characteristics ofpiezoelectric materials in comparative examples 2 to 5 and in examples15, 17, 18, and with respect to temperature dependency in dielectrictangent.

FIGS. 17A, 17B, 17C, and 17D are graphs illustrating characteristics ofpiezoelectric materials in comparative examples 2 to 5 and in examples15, 17, 18, and 21 with respect to temperature dependency inpiezoelectric constant d₃₁.

FIGS. 18A, 18B, 18C, and 18D are graphs illustrating characteristics ofpiezoelectric materials in comparative examples 2 to 5 and in examples15, 17, 18, and with respect to temperature dependency in mechanicalquality factor.

FIG. 19 is a phase diagram illustrating a relationship between x valueand y value (z=0, 0.01, 0.02, and 0.03) of piezoelectric materials inexamples 1 to 60, and 76 to 80 of the present invention and incomparative examples 1 to 23, in which a dotted line indicates thecomposition range of the x value and the y value according to claim 1.

DESCRIPTION OF THE EMBODIMENTS

Various examples, features, and aspects of the invention will bedescribed in detail below with reference to the drawings.

The present invention provides a non-lead piezoelectric material thatcontains (Ba,Ca)(Ti,Zr,Sn)O₃ as a main component and has satisfactorypiezoelectricity and insulating properties. Further, the non-leadpiezoelectric material according to the present invention is higher indensity and mechanical quality factor. The temperature dependency in thepiezoelectric constant is small in an operating temperature range (e.g.,from 20° C. to 45° C.). A piezoelectric material according to thepresent invention has ferroelectric substance characteristics and isemployed for various devices, such as a memory or a sensor.

The piezoelectric material according to the present invention includes amain component containing a perovskite-type metal oxide that can beexpressed using the following general formula (1), a first subcomponentcontaining Mn, a second subcomponent containing Li, and a thirdsubcomponent containing Bi. The content of Mn on a metal basis is notless than 0.04 parts by weight and is not greater than 0.36 parts byweight when the metal oxide is 100 parts by weight. Content α of Li on ametal basis is equal to or less than 0.0012 parts by weight (including 0parts by weight) when the metal oxide is 100 parts by weight. Content βof Bi on a metal basis is not less than 0.042 parts by weight and is notgreater than 0.850 parts by weight when the metal oxide is 100 parts byweight.

General formula (1) (Ba_(1-x)Ca_(x))_(a)(Ti_(1-y-z)Zr_(y)Sn_(z))O₃  (1)

(In the general formula, 0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and0.986≦a≦1.02)

In the present invention, the perovskite-type metal oxide is a metaloxide that has a perovskite-type structure (which may be referred to asa perovskite structure), which is for example described in the fifthedition of Iwanami Dictionary of Physics and Chemistry (Iwanami Shoten,published on Feb. 20, 1998). In general, the metal oxide including theperovskite-type structure can be expressed using a chemical formula ofABO₃. Two chemical elements A and B contained in the perovskite-typemetal oxide are positioned at “A site” and “B site”, respectively, inthe form of ions. Each of the “A site” and the “B site” is a specificposition of the unit cell. For example, in a unit cell of cubic system,the chemical element “A” is positioned at a vertex of a cube. Thechemical element B is positioned at the center of the cube. The element“O” is positioned at the center of a face of the cube, in the form ofanion of oxygen

The content of each subcomponent (e.g., Mn, Bi or Li) “on a metal basis”indicates the following value. For example, a method for obtaining thecontent of Mn includes measuring contents of respective metals Ba, Ca,Ti, Sn, Zr, Mn, Bi, and Li contained in the piezoelectric materialthrough X-ray fluorescence analysis (XRF), ICP emissionspectrophotometric analysis, or atomic absorption analysis. Further, themethod includes calculating a chemical element that constitutes themetal oxide expressed using the general formula (1), as a valuecomparable to an oxide. The method further includes obtaining a ratio ofthe Mn weight when the total weight of respective elements is 100.

The piezoelectric material according to the present invention includesthe perovskite-type metal oxide as a main phase, because theperovskite-type metal oxide has excellent insulating properties. As away of determining whether the perovskite-type metal oxide is the mainphase, for example, it is useful to check whether a maximum diffractionstrength deriving from the perovskite-type metal oxide is equal to orgreater than 100 times a maximum diffraction strength deriving from animpurity phase in the X-ray diffraction. It is desired that thepiezoelectric material is wholly constituted by the perovskite-typemetal oxide because the insulating properties can be maximized. The“main phase” means that the strongest peak of diffraction strength iscaused by the perovskite-type structure in the powder X-ray diffractionof the piezoelectric material. A more desirable phase is a “singlephase” according to which the piezoelectric material is entirelyoccupied by perovskite-type structure crystals.

The general formula (1) indicates that the metal oxide expressed usingthis formula contains Ba and Ca as metal elements positioned at the Asite and Ti, Zr, and Sn as metal elements positioned at the B site.However, Ba and Ca can be partly positioned at the B site. Similarly, Tiand Zr can be partly positioned at the A site. However, it is notdesired that Sn is positioned at the A site because the piezoelectriccharacteristics may deteriorate and the synthesis condition may belimited.

In the general formula (1), the molar ratio between the chemical elementpositioned at the B site and the O element is 1:3. However, even if theelement amount ratio deviates slightly (e.g., in a range from 1.00:2.94to 1.00:3.06), the present invention encompasses such a deviation in therange of the element amount ratio when the metal oxide contains theperovskite-type structure as the main phase.

The piezoelectric material according to the present invention is notrestricted to have a specific form and therefore can be configured asceramics, powder, monocrystal, film, or slurry, although ceramics isdesired. In the following description, “ceramics” represents apolycrystal containing a metal oxide as a basic component and configuredas an aggregate (or a bulk body) of crystal grains sintered through aheat treatment. The “ceramics” according to the present invention can bea fabricated product obtained after the sintering processing.

In the general formula (1), when “x” representing the Ca amount is in arange of 0.09≦x≦0.30, representing the Zr amount is in a range of0.025≦y≦0.085, “z” representing the Sn amount is in a range of 0≦z≦0.02,and “a” representing the molar ratio between the A site and the B siteis in a range of 0.986≦a≦1.02, the piezoelectric constant becomes asatisfactory value in the operating temperature range.

In the general formula (1), the Ca amount “x” is in the range of0.09≦x≦0.30. If the Ca amount “x” is less than 0.09, temperature T_(to)at which a phase transition from a tetragonal to an orthorhombic occursbecomes higher than −10° C. As a result, the temperature dependency inthe piezoelectric constant becomes greater in the operating temperaturerange.

On the other hand, if the Ca amount “x” is greater than 0.30, thepiezoelectric constant decreases due to a generation of CaTiO₃ (i.e.,impurity phase) because Ca is not soluble when the sintering temperatureis equal to or lower than 1400° C. Further, to obtain a desiredpiezoelectric constant, it is desired to set the Ca amount “x” to beequal to or less than 0.26 (i.e., x≦0.26). It is more desirable that theCa amount “x” is equal to or smaller 0.17 (i.e., x≦0.17). In the generalformula (1), the Zr amount “y” is in the range of 0.025<y<0.085. If theZr amount “y” is less than 0.025, the piezoelectricity decreases. If theZr amount “y” is greater than 0.085, the Curie temperature (hereinafter,referred to as T_(C)) may become lower than 90° C. If the Curietemperature T_(c) of the piezoelectric material is less than 90° C.,time degradation of the piezoelectric constant becomes greater when theusage environment is inappropriate. To obtain a satisfactorypiezoelectric constant and set the Curie temperature T_(c) to be notlower than 90° C., the Zr amount “y” is in the range of 0.025≦y≦0.085.

If the Zr amount “y” is equal to or greater than 0.040, it is feasibleto increase the dielectric constant at the room temperature.Accordingly, the piezoelectric constant can be increased. In view of theforegoing, it is desired to set the range of Zr amount “y” to be in arange of 0.040≦y≦0.085. Further, to obtain desired piezoelectricity, itis desired that the range of Zr amount “y” is 0.055≦y≦0.085.

It is desired that the Sn amount “z” is in the range of 0<z≦0.02.Similar to the replacement by Zr, replacing Ti by Sn brings the effectof increasing the dielectric constant at the room temperature andincreasing the piezoelectric constant. Adding Zr or Sn is effective toenhance the dielectric characteristics of the piezoelectric material.However, the phase transition temperature T_(to) of the piezoelectricmaterial increases when Ti is replaced by Zr or Sn. If the phasetransition temperature T_(to) is in the operating temperature range, thetemperature dependency in the piezoelectric constant becomes largerundesirably. Therefore, it is necessary to add Ca to cancel an increasedamount of the phase transition temperature T_(to) if it is increased bythe addition of Zr or Sn, because Ca brings an effect of reducing thetemperature dependency in the piezoelectricity. However, replacing Ti bySn is superior to replacing Ti by Zr in view of suppressing theincreased amount of the phase transition temperature T_(to). Forexample, if 1% of Ti constituting BaTiO₃ is replaced by Zr, the phasetransition temperature T_(to) increases by an amount of approximately12° C. On the other hand, if 1% of Ti is replaced by Sn, the phasetransition temperature T_(to) increases by an amount of approximately 5°C. Therefore, the Ca amount can be effectively reduced by replacing Tiby Sn. However, it is not desired that the Sn amount “z” is less than0.02 (i.e., z>0.02), because the Curie temperature T_(c) becomes lowerthan 100° C. if the Zr amount is inappropriate.

The ratio “a” {a=(Ba+Ca)/(Zr+Ti+Sn)} representing the ratio of the totalmole number of Ba and Ca to the total mole number of Zr, Ti, and Sn isin the range of 0.986<a<1.02. If the ratio “a” is less than 0.986, anabnormal grain growth may occur when the piezoelectric material issintered. Further, an average grain diameter becomes greater than 50 μmand the mechanical strength of the material decreases. If the ratio “a”is greater than 1.02, the density of an obtained piezoelectric materialwill not be sufficiently high. If the density of the piezoelectricmaterial is low, the piezoelectricity decreases. In the presentinvention, a density difference between a test piece having beensintered insufficiently and a test piece having been sinteredinsufficiently is not less than 5%. To obtain a piezoelectric materialthat is higher in density and excellent in mechanical strength, theratio “a” is in the range of 0.986≦a≦1.02.

The piezoelectric material according to the present invention includesMn as the first subcomponent whose content on a metal basis is not lessthan 0.04 parts by weight and is not greater than 0.36 parts by weightwhen the perovskite-type metal oxide expressed using the general formula(1) is 100 parts by weight. If Mn in the above-mentioned range isincluded, the mechanical quality factor increases. However, if thecontent of Mn is less than 0.04 parts by weight, it is unfeasible toobtain the effect of increasing the mechanical quality factor. On theother hand, if the content of Mn is greater than 0.36 parts by weight,the insulation resistance of the piezoelectric material decreases. Whenthe insulation resistance is low, the dielectric tangent at the roomtemperature exceeds 0.01 or the resistivity becomes equal to or lessthan 1G Ωcm. An impedance analyzer is usable to measure the dielectrictangent at the room temperature in a state where an AC electric fieldhaving a field intensity of 10 V/cm is applied at the frequency of 1kHz.

It is desired that the dielectric tangent of the piezoelectric materialaccording to the present invention is equal to or less than 0.006 at thefrequency of 1 kHz. When the dielectric tangent is equal to or less than0.006, it is feasible to obtain a stable operation even when thepiezoelectric material is driven in a state where an electric fieldhaving a maximum field intensity of 500 V/cm is applied to thepiezoelectric material under element driving conditions.

The form of Mn is not limited to a metal and can be an Mn componentcontained in the piezoelectric material. For example, Mn is soluble atthe B site or can be positioned at the grain boundary. Further, it isuseful that an Mn component in the form of metal, ion, oxide, metalsalt, or complex is contained in the piezoelectric material. It isdesirable that the piezoelectric material contains Mn to enhanceinsulating properties and improve sintering easiness. In general, thevalence of Mn is 4+, 2+, or 3+. If a conduction electron is present inthe crystal (e.g., when an oxygen defect is present in the crystal orwhen a donor element occupies the A site), the valence of Mn decreasesfrom 4+ to 3+ or 2+ to trap the conduction electron. Therefore, theinsulation resistance can be improved.

On the other hand, if the valence of Mn is lower than 4+(e.g., when thevalence of Mn is 2+), Mn serves as an acceptor. When the acceptor of Mnis present in a perovskite structured crystal, a hole is generated inthe crystal or an oxygen vacancy is formed in the crystal.

If the valence of added Mn is mostly 2+ or 3+, the insulation resistancedecreases significantly because the hole cannot be compensatedsufficiently by the introduction of the oxygen vacancy. Accordingly, itis desired that most of Mn is 4+. However, a very small amount of Mn hasa valence lower than 4+ and therefore serves as an acceptor thatoccupies the B site of the perovskite structure and may form an oxygenvacancy. Mn having a valence of 2+ or 3+ and the oxygen vacancy form adefect dipole, which can increase the mechanical quality factor of thepiezoelectric material. If a trivalent Bi occupies the A site, Mn tendsto take a valence lower than 4+ to maintain the charge balance.

The valence of a very small amount of Mn added to a non-magnetic(diamagnetic) material can be evaluated by measuring a temperaturedependency in magnetic susceptibility. The magnetic susceptibility canbe measured by a superconducting quantum interference device (SQUID), avibrating sample magnetometer (VSM), or a magnetic balance. TheCurie-Weiss Law that can be expressed by the following general formula 2is usable to express the magnetic susceptibility x obtained through theabove-mentioned measurement.

χ=C/(T−θ)  (Formula 2)

In the formula 2, C represents Curie constant and θ representsparamagnetic Curie temperature.

In general, a very small amount of Mn added to a non-magnetic materialtakes a spin value S=5/2 when the valence is 2+, S=2 when 3+, and S=3/2when 4+. Accordingly, a Curie constant C per unit Mn amount takes avalue corresponding to the spin S value at each valence of Mn. In otherwords, an average valence of Mn contained in a test piece can beevaluated by deriving the Curie constant C from the temperaturedependency in the magnetic susceptibility χ.

To evaluate the Curie constant C, it is desired to set the startingtemperature as low as possible in the measurement of the temperaturedependency in the magnetic susceptibility. In other words, themeasurement becomes difficult if the Mn amount is a very small amountbecause the magnetic susceptibility takes a very small value at acomparatively high temperature (including the room temperature). TheCurie constant C can be derived from the gradient of a straight lineobtainable when a reciprocal 1/χ of the magnetic susceptibility isplotted in relation to the temperature T in the collinear approximation.

The piezoelectric material according to the present invention includesLi as the second subcomponent whose content on a metal basis is equal toor less than 0.0012 parts by weight (including 0 parts by weight) and Bias the third subcomponent whose content on a metal basis is not lessthan 0.042 parts by weight and is not greater than 0.850 parts by weightwhen the perovskite-type metal oxide that can be expressed using thegeneral formula (1) is 100 parts by weight. It is more desirable thatthe content of Li is 0 parts by weight. For example, the ICP-MScomposition analysis is useful to measure the content of Li and Bi inthe piezoelectric material. When the measured value is less than 0.00001parts by weight (measurement limitation), the measured value is regardedas 0 parts by weight. If the content of Li is equal to or less than0.0012 parts by weight, Li has no adverse influence on the piezoelectricconstant. When the content of Li is equal to or less than 0.0012 partsby weight (more preferably, when the content of Li is 0 parts byweight), it is feasible to obtain an excellent interface adherencebetween a piezoelectric material and an electrode when the piezoelectricmaterial is used to fabricate a piezoelectric element.

Further, if the content of Bi is less than 0.042 parts by weight, theeffect of lowering the phase transition temperature and increasing themechanical quality factor cannot be obtained. If the content of Bi isgreater than 0.850 parts by weight, the electromechanical couplingfactor decreases greatly. The reduction amount in this case iscomparable to 30% of a value to be obtained when Bi is not contained.

In the piezoelectric material according to the present invention, Li andBi can be positioned at the grain boundary or can be dissolved in theperovskite-type structure of (Ba,Ca)(Ti,Zr,Sn)O₃.

When Li and Bi are positioned at the grain boundary, the frictionbetween particles decreases and the mechanical quality factor increases.When Li and Bi are dissolved in (Ba,Ca)(Ti,Zr,Sn)O₃ having theperovskite structure, T_(ot) and T_(to) values become lower andtherefore the temperature dependency in the piezoelectric constantbecomes smaller in the operating temperature range. Further, themechanical quality factor can be increased.

For example, X-ray diffraction, electron beam diffraction, electronmicroscope, and ICP-MS are usable to evaluate the place where Li and Biare present.

When Li and Bi are positioned at the B site, the lattice constant of theperovskite structure increases because ion radii of Li and Bi aregreater than those of Ti and Zr.

When Li and Bi are positioned at the A site, the “a” value optimum tosinter a high-density ceramics becomes smaller. In the phase diagram ofBaO and TiO₂, a liquid phase is present at a high temperature on a TiO₂rich side of a composition in which the molar ratio between BaO and TiO₂is 1:1. Therefore, an abnormal grain growth occurs in the sintering ofBaTiO₃ ceramics due to sintering in the liquid phase if the TiO₂component exceeds a stoichiometric ratio. On the other hand, the densityof the ceramics decreases because the sintering does not advancesmoothly if the rate of BaO component is greater. When both Li and Bicomponents are present at the A site, the sintering of ceramics may notadvance smoothly because of excessive components positioned at the Asite. As a result, the density of the ceramics decreases. In such acase, it is useful to lower the “a” value to promote the sintering andobtain a high-density test piece.

For the purpose of easily manufacturing the piezoelectric materialaccording to the present invention or adjusting physical properties ofthe piezoelectric material according to the present invention, it isuseful to replace 1 mol % or less of Ba and Ca by a bivalent metalelement (e.g., Sr). Similarly, it is useful to replace 1 mol % or lessof Ti, Zr, and Sn by a tetravalent metal element (e.g., Hf).

For example, the Archimedes method is usable to measure the density of asintered compact. In the present invention, if a relative density(ρ_(calc.)/ρ_(meas.)), which represents the ratio of theoretical density(ρ_(calc.)) to measured density (ρ_(meas.)), is equal to or greater than95%, it can be regarded that the measured piezoelectric material has asufficiently high density. The theoretical density (ρ_(calc.)) can beobtained with reference to composition and lattice constant of thesintered compact.

The piezoelectricity of a piezoelectric material disappears when thetemperature is equal to or higher than the Curie temperature T_(C). Inthe following description, T_(C) represents the temperature at which thedielectric constant can be maximized around the phase transitiontemperature of a ferroelectric phase (tetragonal phase) and aparaelectric phase (cubic phase). The dielectric constant can bemeasured using, for example, the impedance analyzer at the frequency of1 kHz in a state where the AC electric field having the field intensityof 10 V/cm is applied.

The piezoelectric material according to the present invention causessequential phase transitions to a rhombohedral, an orthorhombic, atetragonal, and a cubic crystal when the temperature increase startsfrom a lower level. The phase transition referred to in the presentexample is limited to a phase transition from the orthorhombic to thetetragonal or a phase transition from the tetragonal to theorthorhombic. The phase transition temperature can be evaluated using ameasuring method similar to that employed for the Curie temperature. Thephase transition temperature refers to the temperature at which aderivative, which is obtainable by differentiating the dielectricconstant by the test piece temperature, can be maximized. For example,X-ray diffraction, electron beam diffraction, and Raman scattering areusable to evaluate the crystal system.

The mechanical quality factor decreases when a domain wall vibrates. Ingeneral, the density of the domain wall increases and the mechanicalquality factor decreases when the complicatedness of a domain structureincreases. The crystal orientation of spontaneous polarization of anorthorhombic or tetragonal perovskite structure is <110> or <100> whenexpressed according to the pseudo-cubic crystal notation. Morespecifically, compared to an orthorhombic structure, a tetragonalstructure has a lower spatial flexibility in spontaneous polarization.Therefore, the tetragonal structure is superior to the orthorhombicstructure in that the domain structure becomes simple and the mechanicalquality factor becomes higher even when the composition is identical.Accordingly, it is desired that the piezoelectric material according tothe present invention has the tetragonal structure, rather than theorthorhombic structure, in the operating temperature range.

The dielectric constant and the electromechanical coupling factor aremaximized around the phase transition temperature. On the other hand,the Young's modulus is minimized. The piezoelectric constant can beexpressed as a function using the above-mentioned three parameters. Thepiezoelectric constant takes an extreme value or an inflection pointaround the phase transition temperature. Therefore, if a phasetransition occurs in the operating temperature range of a device, itbecomes difficult to control the device because performances of thedevice extremely vary depending on the temperature or the resonancefrequency varies depending on the temperature. Accordingly, it isdesired that the phase transition (i.e., the maximum factor that causesa variation in piezoelectric performances) is not in the operatingtemperature range. If the phase transition temperature deviates from theoperating temperature range, the temperature dependency in piezoelectricperformances decreases in the operating temperature range.

The piezoelectric material according to the present invention includes afourth subcomponent containing Mg. It is desired that the content of thefourth subcomponent on a metal basis is equal to or less than 0.10 partsby weight (excluding 0 parts by weight) when the perovskite-type metaloxide that can be expressed using the general formula (1) is 100 partsby weight.

When the content of Mg is greater than 0.10 parts by weight, themechanical quality factor becomes smaller (e.g., less than 600). If thepiezoelectric material is used to fabricate a piezoelectric element andthe fabricated element is driven as a resonance device, powerconsumption increases when the mechanical quality factor is small. It isdesired that the mechanical quality factor is equal to or greater than800. It is more desirable that the mechanical quality factor is equal toor greater than 1000. To obtain a more desirable mechanical qualityfactor, it is desired that the content of Mg is equal to or less than0.05 parts by weight.

The form of Mg can be a Mg component contained in piezoelectricmaterial. The form of Mg is not limited to a metal Mg. For example, Mgis soluble at the A site or the B site of the perovskite structure orcan be positioned at the grain boundary. Alternatively, it is usefulthat an Mg component in the form of metal, ion, oxide, metal salt, orcomplex is contained in the piezoelectric material.

It is desired that the piezoelectric material according to the presentinvention includes a fifth subcomponent that contains at least one of Siand B. It is desired that the content of the fifth subcomponent on ametal basis is not less than 0.001 parts by weight and is not greaterthan 4.000 parts by weight when the metal oxide that can be expressedusing the general formula (1) is 100 parts by weight. The fifthsubcomponent has a role of lowering the sintering temperature of thepiezoelectric material according to the present invention. When thepiezoelectric material is incorporated in a multilayered piezoelectricelement, the piezoelectric material is sintered together with anelectrode material in the manufacturing process thereof. In general, theheat-resistant temperature of an electrode material is lower than thatof the piezoelectric material. Therefore, if the sintering temperatureof the piezoelectric material can be reduced, the energy required tosinter the piezoelectric material can be reduced and the number ofemployable electrode materials can be increased.

Further, Si and B are segregated at the grain boundary of thepiezoelectric material. Therefore, leakage current flowing along thegrain boundary reduces and the resistivity becomes higher.

When the content of the fifth subcomponent is less than 0.001 parts byweight, the effect of lowering the sintering temperature cannot beobtained. When the content of the fifth subcomponent is greater than4.000 parts by weight, the dielectric constant decreases and, as aresult, the piezoelectricity decreases. When the content of the fifthsubcomponent is not less than 0.001 parts by weight and is not greaterthan 4.000 parts by weight, the reduction of piezoelectricity can besuppressed to 30% or less and the sintering temperature can be reduced.In particular, it is more desirable to set the content of the fifthsubcomponent to be not less than 0.05 parts by weight because sinteringa high-density ceramics at a sintering temperature lower than 1250° C.becomes feasible. Further, it is more desirable to set the content ofthe fifth subcomponent to be not less than 0.09 parts by weight and notgreater than 0.15 parts by weight because the sintering can be performedat 1200° C. or lower and the reduction of piezoelectricity can besuppressed to 20% or less.

It is desired that the piezoelectric material according to the presentinvention satisfies a relationship y+z≦(11x/14)−0.037 in the generalformula (1). When x, y, and z satisfy the above-mentioned relationship,the phase transition temperature T_(to) becomes lower than −20° C. andthe temperature dependency in the piezoelectric constant becomes smallerin the operating temperature range.

It is desired that the Curie temperature of the piezoelectric materialaccording to the present invention is equal to or higher than 100° C.When the Curie temperature is equal to or higher than 100° C., thepiezoelectric material according to the present invention can possess astable piezoelectric constant and an adequate mechanical quality factorwhile maintaining the piezoelectricity satisfactorily even in a severetemperature condition comparable to the temperature inside a vehicle(e.g., 80° C.) in the summer season.

A method for manufacturing the piezoelectric material according to thepresent invention is not specifically limited.

In manufacturing a piezoelectric ceramics, a general method includingsintering a solid powder (e.g., oxide, carbonate, nitrate, or oxalate)containing constituent elements under a normal pressure is employable.Appropriate metal compounds, such as Ba compound, Ca compound, Ticompound, Zr compound, Sn compound, Mn compound, Li compound, and Bicompound, are usable as raw materials for the piezoelectric materialaccording to the present invention.

For example, barium hydroxide, barium carbonate, barium oxalate, bariumacetate, barium nitrate, barium titanate, barium zirconate, and bariumtitanate zirconate are Ba compounds usable in the present invention.

For example, calcium oxide, calcium carbonate, calcium oxalate, calciumacetate, calcium titanate, and calcium zirconate are Ca compounds usablein the present invention.

For example, titanium oxide, barium titanate, barium titanate zirconate,and calcium titanate are Ti compounds usable in the present invention.

For example, zirconium oxide, barium zirconate, barium titanatezirconate, and calcium zirconate are Zr compounds usable in the presentinvention.

For example, tin oxide, barium stannate, and calcium stannate are Sncompounds usable in the present invention.

For example, manganese carbonate, manganese monoxide, manganese dioxide,tetramanganese trioxide, and manganese acetate are Mn compounds usablein the present invention.

For example, lithium carbonate and lithium bismuthic acid are Licompounds usable in the present invention.

For example, bismuth oxide and lithium bismuthic acid are Bi compoundsusable in the present invention.

Further, a raw material to be required to adjust “a”{a=(Ba+Ca)/(Zr+Ti+Sn)} representing the ratio of the total mole numberof Ba and Ca to the total mole number of Ti, Zr, and Sn of thepiezoelectric ceramics according to the present invention is notspecifically limited. Each of the above-mentioned Ba compounds, Cacompounds, Ti compounds, Zr compounds, and Sn compounds brings similareffects.

A method for granulating the raw material powder for the piezoelectricceramics according to the present invention is not specifically limited.A binder usable in the granulation is, for example, polyvinyl alcohol(PVA), polyvinyl butylal (PVB), or acrylic resin. It is desired that theaddition amount of the binder is in a range from 1 parts by weight to 10parts by weight. Further, it is desired to set the addition amount ofthe binder to be in a range from 2 parts by weight to 5 parts by weightbecause the molding density can be increased. It is useful to granulatea mixed powder that can be obtained by mechanically mixing theabove-mentioned Ba compound, Ca compound, Ti compound, Zr compound, Sncompound, and Mn compound. It is also useful to calcinate theabove-mentioned compounds in a temperature range of 800 to 1300° C.before these compounds are granulated. Further, it is useful to add theMn compound and a binder simultaneously to the calcinated mixture of theabove-mentioned Ba compound, Ca compound, Ti compound, Zr compound, Sncompound, Li compound, and Bi compound. Further, if it is required toobtain a granulated powder having a uniform grain diameter, the mostdesirable granulation method is a spray-dry method.

A method for fabricating the piezoelectric ceramics compact according tothe present invention is not specifically limited. The compact is asolid body that can be fabricated from a raw material powder, agranulated powder, or slurry. The fabrication of the compact can berealized, for example, by uniaxial pressurization working, coldhydrostatic pressure working, warm hydrostatic pressure working, castmolding, or extrusion molding.

A method for sintering the piezoelectric ceramics according to thepresent invention is not specifically limited. The sintering method is,for example, a sintering method using an electric furnace, a sinteringmethod using a gas furnace, an electric heating method, a microwavesintering method, a milliwave sintering method, or a hot isotropic press(HIP). The electric furnace based sintering and the gas furnace basedsintering can be realized by a continuous furnace or a batch furnace.

The above-mentioned sintering method does not specifically limit thesintering temperature of the ceramics. However, it is desired that thesintering temperature is sufficient to cause each compound to react andcause the crystal to grow. If the ceramics is required to have a graindiameter of 3 μm to 30 μm, the desirable sintering temperature is notlower than 1100° C. and is not higher than 1550° C. It is more desirableto set the sintering temperature to be not lower than 1100° C. and nothigher than 1380° C. The piezoelectric ceramics having been sintered inthe above-mentioned temperature range demonstrates satisfactorypiezoelectric performances.

If it is required to constantly stabilize the characteristics of apiezoelectric ceramics obtained through the sintering processing, it isdesired that the sintering time is not shorter than two hours and notlonger than 24 hours under a condition that the sintering temperature ismaintained within the above-mentioned range.

Although a conventionally known sintering method (e.g., the two-stepsintering method) is employable, it is useful to select an appropriatemethod that does not cause any abrupt change in the temperature when theproductivity is taken into consideration.

When the piezoelectric ceramics is subjected to a polish working, it isdesired that the piezoelectric ceramics is subsequently subjected to aheat treatment at 1000° C. or higher. When the piezoelectric ceramics ismechanically polished, a significant residual stress is generated in thepiezoelectric ceramics. However, the residual stress can be reduced byperforming the heat treatment at 1000° C. or higher. The piezoelectriccharacteristics of the piezoelectric ceramics can be further improved.Further, performing the above-mentioned heat treatment is effective toremove the raw material powder (including barium carbonate) that maydeposit along the grain boundary portion. Although the time required tocomplete the heat treatment is not specifically limited, it is desiredthat the heat treatment time is equal to or greater than one hour.

If the crystal grain diameter of the piezoelectric material according tothe present invention exceeds 50 μm, the material strength may beinsufficient for a cut working and a polish working. Further, thepiezoelectricity deteriorates if the grain diameter is less than 0.3 μm.Accordingly, it is desired that an average grain diameter range is notless than 0.3 μm and is not greater than 50 μm. It is more desirablethat the grain diameter range is not less than 3 μm and is not greaterthan 30 μm.

In the present invention, the “grain diameter” is a “projected areadiameter” that is generally referred to in a microscopic observationmethod. More specifically, the “grain diameter” represents the diameterof a perfect circle that has an area comparable to the projected area ofthe crystal grain. A method for measuring the grain diameter accordingto the present invention is not specifically limited. For example, thegrain diameter can be obtained by performing image processing on aphotographic image of a surface of a piezoelectric material that can becaptured by a polarizing microscope or a scanning electron microscope.It may be useful to selectively use either the optical microscope or theelectron microscope because the optimum magnification is variabledepending on the diameter of a target particle. It is also useful toobtain an equivalent circle diameter based an image of a polishedsurface or a cross section of the material.

When the piezoelectric material according to the present invention isused to fabricate a film on a substrate, it is desired that thethickness of the piezoelectric material is not less than 200 nm and isnot greater than 10 μm. It is more desirable that the thickness of thepiezoelectric material is not less than 300 nm and is not greater than 3μm. When the film thickness of the piezoelectric material is not lessthan 200 nm and is not greater than 10 μm, the piezoelectric element canpossess a sufficient electromechanical transducing function.

A film forming method is not specifically limited. For example, achemical solution deposition (CSD) method, a sol-gel method, a metalorganic chemical vapor deposition (MOCVD) method, a sputtering method, apulsed laser deposition (PLD) method, a hydrothermal method, an aerosoldeposition (AD) method are usable to form a film. When the film to beformed is a multilayered film, the most desirable method selectable fromthe above-mentioned methods is the chemical solution deposition methodor the sputtering method. The chemical solution deposition method or thesputtering method is preferably used to form a film having a large area.A monocrystal substrate being cut and polished along a (001) or (110)plane is preferably used as a substrate of the piezoelectric materialaccording to the present invention. Using the monocrystal substratebeing cut and polished along a specific crystal plane is useful in thata piezoelectric material film to be provided on a substrate surface canbe strongly orientated in the same direction.

Hereinafter, a piezoelectric element using the piezoelectric materialaccording to the present invention is described in detail below.

FIG. 1 schematically illustrates a configuration of the piezoelectricelement according to an example of the present invention. Thepiezoelectric element according to the present invention includes afirst electrode 1, a piezoelectric material portion 2, and a secondelectrode 3. The piezoelectric element is characterized in that thepiezoelectric material portion 2 is constituted by the piezoelectricmaterial according to the present invention.

When the piezoelectric material according to the present invention isincorporated into a piezoelectric element including at least the firstelectrode and the second electrode, the piezoelectric element canpossess evaluable piezoelectric characteristics. Each of the firstelectrode and the second electrode is an electrically conductive layerhaving a thickness of 5 nm to 10 μm. The material of the first andsecond electrodes is not specifically limited and can be any materialordinarily usable for piezoelectric elements. For example, metals suchas Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu andtheir compounds are usable.

Each of the first electrode and the second electrode can be formed as asingle layer made of only one material selected from the above-mentionedexamples or can be formed as a multilayered electrode including at leasttwo materials. Further, the material of the first electrode can bedifferentiated from the material of the second electrode.

The method for manufacturing the first electrode and the secondelectrode is not specifically limited. For example, the manufacturingmethod can include baking a metal paste. Further, the sputtering methodor the vapor deposition method is usable. Further, patterning the firstelectrode and the second electrode into desired shapes is also useful.

It is more desirable that polarization axes of the piezoelectric elementare uniformly oriented in a predetermined direction. When thepolarization axes are uniformly oriented in the predetermined direction,the piezoelectric constant of the piezoelectric element becomes greater.

A method for polarizing the piezoelectric element is not specificallylimited. The polarization processing can be performed in the atmosphereor can be performed in a silicone oil. It is desired that thepolarization temperature is in a range from 60° C. to 150° C. However,optimum conditions are slightly variable depending on actualcompositions of a piezoelectric material that is employed to constitutean element. Further, it is desired that the electric field to be appliedin the polarization processing is in a range from 600 V/mm to 2.0 kV/mm.

The piezoelectric constant and the electromechanical quality factor ofthe piezoelectric element can be calculated based on measurement resultsof the resonance frequency and the antiresonance frequency obtained by acommercially available impedance analyzer, with reference to standardsof Japan Electronics and Information Technology Industries Association(JEITA EM-4501). Hereinafter, the above-mentioned method is referred toas a resonant-antiresonant method.

Next, a multilayered piezoelectric element that can be fabricated usingthe piezoelectric material according to the present invention isdescribed in detail below.

<Multilayered Piezoelectric Element>

The multilayered piezoelectric element according to the presentinvention is a multilayered piezoelectric element that includes aplurality of piezoelectric material layers and a plurality of electrodesincluding at least one internal electrode, which are alternatelymultilayered. The piezoelectric material layer that constitutes themultilayered piezoelectric element is characterized by being made of thepiezoelectric material according to the present invention.

FIGS. 2A and 2B are cross-sectional views schematically illustratingexample configurations of the multilayered piezoelectric elementaccording to an example of the present invention. The multilayeredpiezoelectric element according to the present invention includespiezoelectric material layers 54 and electrodes including an internalelectrode 55. In other words, the multilayered piezoelectric elementaccording to the present invention is characterized by includingpiezoelectric material layers and at least one layered electrode thatare alternately multilayered and the piezoelectric material layer 54 ismade of the above-mentioned piezoelectric material. The electrodes ofthe multilayered piezoelectric element can include external electrodes,such as a first electrode 51 and a second electrode 53, in addition tothe internal electrode 55.

FIG. 2A illustrates an example of the multilayered piezoelectric elementaccording to the present invention, which includes two piezoelectricmaterial layers 54 and a single internal electrode 55 that arealternately multilayered in such a way as to constitute a multilayeredstructure sandwiched between the first electrode 51 and the secondelectrode 53. The number of the piezoelectric material layers and theinternal electrodes can be increased as illustrated in FIG. 2B. Thenumber of constituent layers is not limited to a specific value. Themultilayered piezoelectric element illustrated in FIG. 2B includes ninepiezoelectric material layers 504 and eight internal electrodes 505 thatare alternately multilayered in such a way as to constitute amultilayered structure sandwiched between the first electrode 501 andthe second electrode 503. The multilayered piezoelectric elementillustrated in FIG. 2B further includes two external electrodes 506 aand 506 b that electrically connect the alternately disposed internalelectrodes.

The internal electrodes 55 and 505 and the external electrodes 506 a and506 b are not always similar to the piezoelectric material layers 54 and504 in size and shape. Each electrode can be further divided into aplurality of subelectrodes.

Each of the internal electrodes 55 and 505, the external electrodes 506a and 506 b, the first electrodes 51 and 501, and the second electrodes53 and 503 is constituted by an electrically conductive layer having athickness of 5 nm to 10 μm. The material of each electrode is notspecifically limited and can be an ordinary material that can be usedfor a piezoelectric element. For example, metals such as Ti, Pt, Ta, Ir,Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu and their compounds areusable as the electrode constituting the multilayered piezoelectricelement. One material or a mixture (or an alloy) containing two or morematerials selected from the above-mentioned group can be used as theinternal electrodes 55 and 505 and the external electrodes 506 a and 506b. Further, two or more materials selected form the above-mentionedgroup can be multilayered. Further, a plurality of electrodes can bemade of mutually different materials. When the cheapness of theelectrode material is taken into consideration, it is desired that theinternal electrodes 55 and 505 include at least one of Ni and Cu. Whenthe internal electrodes 55 and 505 use at least one of Ni and Cu, it isdesired that the multilayered piezoelectric element according to thepresent invention is sintered in a reducing atmosphere.

In the multilayered piezoelectric element according to the presentinvention, it is desired that the internal electrode includes Ag and Pdand a relationship 0.25≦M1/M2≦4.0 is satisfied with respect to a weightratio M1/M2, in which M1 represents the content of Ag and M2 representsthe content of Pd. It is not desired to set the weight ratio M1/M2 to beless than 0.25 because the sintering temperature of the internalelectrode becomes higher. Further, it is not desired to set the weightratio M1/M2 to be greater than 4.0 because the internal electrodebecomes an island shape. In other words, the internal electrode surfacebecomes ununiform. It is more desirable that a relationship0.3≦M1/M2≦3.0 is satisfied with respect to the weight ratio M1/M2.

As illustrated in FIG. 2B, a plurality of electrodes including theinternal electrode 505 can be electrically connected to each other toequalize the driving voltage phase. For example, each internal electrode505 a can be electrically connected to the first electrode 501 via theexternal electrode 506 a. Each internal electrode 505 b can beelectrically connected to the second electrode 503 via the externalelectrode 506 b. The internal electrodes 505 a and the internalelectrodes 505 b can be alternately disposed. Further, the way ofelectrically connecting electrodes is not limited to a specificstructure. For example, it is useful to provide a dedicated electrode orwiring on a side surface of the multilayered piezoelectric element torealize a comparable electrical connection between electrodes. It isalso useful to provide a through-hole that extends across a plurality ofpiezoelectric material layers and fill the inside space thereof with anelectrically conductive material to realize a comparable electricalconnection between electrodes.

<Liquid Discharge Head>

A liquid discharge head according to the present invention ischaracterized by a liquid chamber that is equipped with a vibrating unitin which the above-mentioned piezoelectric element or theabove-mentioned multilayered piezoelectric element is disposed and adischarge port that communicates with the liquid chamber. The liquid tobe discharged from the liquid discharge head according to the presentinvention is not limited to a specific fluid. For example, the liquiddischarge head according to the present invention can discharge aqueousliquid (e.g., water, ink, or fuel) or non-aqueous liquid.

FIGS. 3A and 3B schematically illustrate a configuration of the liquiddischarge head according to an example of the present invention. Asillustrated in FIGS. 3A and 3B, the liquid discharge head according tothe present invention includes a piezoelectric element 101 according tothe present invention. The piezoelectric element 101 includes a firstelectrode 1011, a piezoelectric member 1012, and a second electrode1013. The piezoelectric member 1012 is formed as a patterning, ifnecessary, as illustrated in FIG. 3B.

FIG. 3B is a schematic diagram illustrating a liquid discharge head. Theliquid discharge head includes a plurality of discharge ports 105,individual liquid chambers 102, continuous holes 106 each connecting theindividual liquid chamber 102 to the corresponding discharge port 105, aliquid chamber bulkhead 104, a common liquid chamber 107, a vibrationplate 103, and the piezoelectric element 101. The piezoelectric element101 illustrated in FIGS. 3A and 3B has a rectangular shape. However, thepiezoelectric element 101 can be configured to have an elliptic,circular, or parallelogrammatic shape. In general, the piezoelectricmember 1012 has a shape similar to that of the individual liquid chamber102.

A peripheral structure of the piezoelectric element 101 included in theliquid discharge head according to the present invention is described indetail below with reference to FIG. 3A. FIG. 3A is a cross-sectionalview of the piezoelectric element illustrated in FIG. 3B, taken alongthe width direction. The cross-sectional shape of the piezoelectricelement 101 is not limited to an illustrated rectangular shape and canbe a trapezoidal or reverse trapezoidal shape.

In FIGS. 3A and 3B, the first electrode 1011 serves as a lower electrodeand the second electrode 1013 serves as an upper electrode. However, thefirst electrode 1011 and the second electrode 1013 are not limited theabove-mentioned arrangement. For example, the first electrode 1011 canbe used as the upper electrode and the second electrode 1013 can be usedas the lower electrode. Further, it is useful to provide a buffer layer108 between the vibration plate 103 and the lower electrode. Theabove-mentioned differences in the names to be referred to are dependenton the manufacturing method of an individual device. In any case,effects of the present invention can be obtained.

In the liquid discharge head, the vibration plate 103 moves in theup-and-down direction in response to an expansion/contraction motion ofthe piezoelectric member 1012 in such a way as to pressurize the liquidin the individual liquid chamber 102. As a result, the liquid can bedischarged from the discharge port 105. The liquid discharge headaccording to the present invention can be incorporated into a printerand can be used in the manufacturing of an electronic device. Thethickness of the vibration plate 103 is not less than 1.0 μm and is notgreater than 15 μm. It is desired to set the thickness of the vibrationplate 103 to be not less than 1.5 μm and not greater than 8 μm. It isdesired that the vibration plate is made of Si, although the material ofthe vibration plate is not limited to a specific material. Further, thevibration plate can be configured as a boron (or phosphorus) dopedvibration plate if the vibration plate contains Si. Further, the bufferlayer and the electrode provided on the vibration plate can beconfigured as a part of the vibration plate. The thickness of the bufferlayer 108 is not less than 5 nm and is not greater than 300 nm. It isdesired to set the thickness of the buffer layer 108 to be not less than10 nm and is not greater than 200 nm. The size of the discharge port 105is not less than 5 μm and is not greater than 40 μm, when measured as anequivalent circle diameter. The discharge port 105 can be configured tohave a circular shape, a star shape, a rectangular shape, or atriangular shape.

<Liquid Discharge Apparatus>

Next, a liquid discharge apparatus according to the present invention isdescribed in detail below. The liquid discharge apparatus according tothe present invention includes a portion on which an image transferredmedium is placed and the above-mentioned liquid discharge head.

FIGS. 4 and 5 illustrate an inkjet recording apparatus as an example ofthe liquid discharge apparatus according to the present invention. FIG.5 illustrates a state where exterior parts 882 to 885 and 887 areremoved from a liquid discharge apparatus (i.e., an inkjet recordingapparatus) 881 illustrated in FIG. 4. The inkjet recording apparatus 881includes an automatic feeding unit 897 that can automatically feed arecording paper (i.e., the image transferred medium) into an apparatusmain body 896. Further, the inkjet recording apparatus 881 includes aconveyance unit 899 that can guide a recording paper fed from theautomatic feeding unit 897 to a predetermined recording position andfurther guide the recording paper from the recording position to anoutlet port 898. The inkjet recording apparatus 881 further includes arecording unit 891 that can perform recording on the recording paperconveyed to the recording position and a recovery unit 890 that canperform recovery processing for the recording unit 891. The recordingunit 891 includes a carriage 892 in which the liquid discharge headaccording to the present invention is placed in such a way as to movealong a rail.

In the above-mentioned inkjet recording apparatus, the carriage 892moves along the rail in response to an electric signal supplied from acomputer and the piezoelectric material causes a displacement when adriving voltage is applied to electrodes that sandwich the piezoelectricmaterial. The displacement of the piezoelectric material presses theindividual liquid chamber 102 via the vibration plate 103 illustrated inFIG. 3B to discharge an ink from the discharge port 105 to performprinting. The liquid discharge apparatus according to the presentinvention can uniformly discharge liquid at a higher speed and candownsize the apparatus body.

The liquid discharge apparatus according to the present invention is notlimited to the above-mentioned printer and can be configured as afacsimile machine, a multifunction peripheral, a copy machine, or anyother printing apparatus. Further, the liquid discharge apparatusaccording to the present invention can be configured as an industrialliquid discharge apparatus or a target drawing apparatus.

In addition, a user can select a desired image transferred mediumaccording to an intended purpose. The liquid discharge head can moverelative to an image transferred medium placed on a stage that serves asthe image transferred medium placement portion.

<Ultrasonic Motor>

An ultrasonic motor according to the present invention is characterizedby a vibrating body in which the above-mentioned piezoelectric elementor the above-mentioned multilayered piezoelectric element is disposedand a moving body that contacts the vibrating body. FIGS. 6A and 6Bschematically illustrate configuration examples of the ultrasonic motoraccording to an example of the present invention. FIG. 6A illustrates anexample of the ultrasonic motor that includes a single-plate typepiezoelectric element according to the present invention. The ultrasonicmotor illustrated in FIG. 6A includes an oscillator 201, a rotor 202contacting a sliding surface of the oscillator 201 under a pressingforce applied by a compression spring (not illustrated), and an outputshaft 203 integrally formed with the rotor 202. The oscillator 201includes an elastic metal ring 2011, a piezoelectric element 2012 (i.e.,a piezoelectric element according to the present invention), and anorganic adhesive 2013 (e.g., an epoxy type or a cyanoacrylate type) thatconnects the piezoelectric element 2012 to the elastic ring 2011. Thepiezoelectric element 2012 according to the present invention isconstituted by a piezoelectric material sandwiched by a first electrode(not illustrated) and a second electrode (not illustrated). Whentwo-phase alternating voltages having a phase difference comparable toodd times of n/2 is applied to the piezoelectric element according tothe present invention, a curved traveling wave appears on the oscillator201 and each point on the sliding surface of the oscillator 201 causesan elliptic motion. If the rotor 202 is pressed against the slidingsurface of the oscillator 201, the rotor 202 receives a frictional forcefrom the oscillator 201 and rotates in a direction opposed to the curvedtraveling wave. A driven member (not illustrated) is connected to theoutput shaft 203 and is driven by a rotational force of the rotor 202. Apiezoelectric transversal effect obtainable when a voltage is applied toa piezoelectric material causes the piezoelectric material to stretch.In a case where an elastic body (e.g., a metallic member) is connectedto a piezoelectric element, the elastic body is bent in accordance withan expansion and contraction motion of the piezoelectric material. Theultrasonic motor illustrated in FIG. 6A is operable based on theabove-mentioned principle. FIG. 6B illustrates another example of theultrasonic motor that includes a piezoelectric element having amultilayered structure. An oscillator 204 includes a multilayeredpiezoelectric element 2042 sandwiched between cylindrical elastic metalbodies 2041. The multilayered piezoelectric element 2042 is constitutedby a plurality of multilayered piezoelectric materials (notillustrated). The multilayered piezoelectric element 2042 includes afirst electrode and a second electrode formed on outer surfaces of themultilayered body and an internal electrode provided in the multilayeredbody. The elastic metal bodies 2041 are tightened by means of bolts tofirmly hold the piezoelectric element 2042 between them in such a way asto constitute the oscillator 204. If alternating voltages having a phasedifference therebetween are applied to the piezoelectric element 2042,the oscillator 204 generates two types of vibrations that are mutuallyperpendicular. The above-mentioned vibrations, when combined together,can drive a front end portion of the oscillator 204 and therefore canform a circular vibration. A circular groove is formed at an upper partof the oscillator 204 so that the vibratory displacement can beincreased. A pressing spring 206 presses the rotor 205 against theoscillator 204 to obtain a driving frictional force. The rotor 205 isrotatable and supported by a bearing.

<Optical Device>

Next, an optical device according to the present invention is describedin detail below. The optical device according to the present inventionis characterized by a driving unit that includes the ultrasonic motor.

FIG. 7 is an essential cross-sectional view illustrating aninterchangeable lens barrel of a single lens reflex camera, as anexample of the optical device according to an example of the presentinvention. FIG. 8 is an exploded perspective view illustrating theinterchangeable lens barrel of the single lens reflex camera, as anexample of the optical device according to a preferred example of thepresent invention. A fixed barrel 712, a rectilinear guide barrel 713,and a front group lens barrel 714 (i.e., fixing members of theinterchangeable lens barrel) are fixed to a camera detachment mount 711.

A rectilinear guide groove 713 a extending in the optical axis directionof a focus lens 702 is formed on the rectilinear guide barrel 713. Anaxial screw 718 fixes cam rollers 717 a and 717 b to a rear group lensbarrel 716 that holds the focus lens 702. Each of the cam rollers 717 aand 717 b protrudes outwardly in the radial direction. The cam roller717 a is coupled with the rectilinear guide groove 713 a.

A cam ring 715 is rotatable and coupled with an inner surface of therectilinear guide barrel 713. A relative movement between therectilinear guide barrel 713 and the cam ring 715 in the optical axisdirection is regulated when a roller 719 fixed to the cam ring 715 iscoupled with a circular groove 713 b of the rectilinear guide barrel713. A cam groove 715 a dedicated to the focus lens 702 is formed on thecam ring 715. The above-mentioned cam roller 717 b is simultaneouslycoupled with the cam groove 715 a.

A rotation transmission ring 720 is disposed on an outer surface of thefixed barrel 712. A ball race 727 holds the rotation transmission ring720 in such a way as to be rotatable relative to the fixed barrel 712 ata predetermined position. A roller 722, which is freely rotatable, isheld by a shaft 720 f that radially extends from the rotationtransmission ring 720. A large-diameter portion 722 a of the roller 722is brought into contact with a mount side surface 724 b of a manualfocus ring 724. Further, a small-diameter portion 722 b of the roller722 is brought into contact with a joint member 729. Six rollers 722,each having the above-mentioned configuration, are disposed at equalintervals around an outer surface of the rotation transmission ring 720.

A low-friction sheet (e.g., a washer member) 733 is disposed at an innercylindrical portion of the manual focus ring 724. The low-friction sheetis sandwiched between a mount end surface 712 a of the fixed barrel 712and a front end surface 724 a of the manual focus ring 724. Further, anouter cylindrical surface of the low-friction sheet 733 has a ring shapeand is radially coupled with an inner diameter portion 724 c of themanual focus ring 724. Further, the inner diameter portion 724 c of themanual focus ring 724 is radially coupled with an outer-diameter portion712 b of the fixed barrel 712. The low-friction sheet 733 has a role ofreducing the friction in a rotary ring mechanism in which the manualfocus ring 724 is configured to rotate around the optical axis relativeto the fixed barrel 712.

A wave washer 726 presses an ultrasonic motor 725 toward the front sideof the lens. The pressing force of the wave washer 726 can hold thelarge-diameter portion 722 a of the roller 722 and the mount sidesurface 724 b of the manual focus ring 724 in the contact state.Similarly, the force of the wave washer 726 pressing the ultrasonicmotor 725 toward the front side of the lens can appropriately press thesmall-diameter portion 722 b of the roller 722 against the joint member729 so as to maintain the contact state. A washer 732, which isconnected to the fixed barrel 712 by bayonet coupling, regulates thewave washer 726 when it moves in the mount direction. A spring force(i.e., a biasing force) generated by the wave washer 726 can betransmitted to the ultrasonic motor 725 and further to the roller 722.The transmitted force causes the manual focus ring 724 to press themount end surface 712 a of the fixed barrel 712. More specifically, inthe incorporated state, the manual focus ring 724 is pressed against themount end surface 712 a of the fixed barrel 712 via the low-frictionsheet 733.

Accordingly, when a control unit (not illustrated) drives the ultrasonicmotor 725 to cause a rotation relative to the fixed barrel 712, theroller 722 rotates around the central axis of the shaft 720 f becausethe joint member 729 frictionally contacts the small-diameter portion722 b of the roller 722. When the roller 722 rotates around the shaft720 f, the rotation transmission ring 720 rotates around the opticalaxis (which is referred to as an auto-focusing operation).

Further, if a rotational force around the optical axis is given to themanual focus ring 724 from a manual operation input unit (notillustrated), the roller 722 rotates around the shaft 720 f due to africtional force because the mount side surface 724 b of the manualfocus ring 724 is pressed against the large-diameter portion 722 a ofthe roller 722. When the large-diameter portion 722 a of the roller 722rotates around the shaft 720 f, the rotation transmission ring 720rotates around the optical axis. In this case, a friction holding forceacting between a rotor 725 c and a stator 725 b prevents the ultrasonicmotor 725 from rotating (which is referred to as a manual focusingoperation).

Two focus keys 728, being positioned in an opposed relationship, areattached to the rotation transmission ring 720. The focus key 728 iscoupled with a cutout portion 715 b provided at a front end of the camring 715. Accordingly, if the rotation transmission ring 720 rotatesaround the optical axis when an auto-focusing operation or a manualfocusing operation is performed, the rotational force thereof istransmitted to the cam ring 715 via the focus key 728. When the cam ring715 rotates around the optical axis, the cam roller 717 b moves the reargroup lens barrel 716 forward and rearward along the cam groove 715 a ofthe cam ring 715 in a state where the rotation of the rear group lensbarrel 716 is regulated by the cam roller 717 a and the rectilinearguide groove 713 a. Thus, the focus lens 702 is driven and a focusingoperation is performed.

The optical device according to the present invention is not limited tothe above-mentioned interchangeable lens barrel applicable to a singlelens reflex camera, and can be configured as a compact camera, anelectronic still camera, a camera-equipped portable informationterminal, or any other type of optical device that includes anultrasonic motor serving as the above-mentioned driving unit.

<Vibrating Apparatus and Dust Removing Apparatus>

A vibrating apparatus that is configured to convey and remove particles,powder, and droplet can be widely used in electronic devices.

Hereinafter, a dust removing apparatus using the piezoelectric elementaccording to the present invention, which is an example of the vibratingapparatus according to the present invention, is described in detailbelow.

The dust removing apparatus according to the present invention ischaracterized by a vibrating body that includes the piezoelectricelement or the multilayered piezoelectric element disposed on avibration plate.

FIGS. 9A and 9B schematically illustrate a dust removing apparatus 310according to an example of the present invention. The dust removingapparatus 310 includes a pair of planar piezoelectric elements 330 and avibration plate 320. Each piezoelectric element 330 can be configured asthe multilayered piezoelectric element according to the presentinvention. The material of the vibration plate 320 is not required tohave a specific quality. However, a light transmissive material or alight reflective material is usable for the vibration plate 320 when thedust removing apparatus 310 is used in an optical device.

FIGS. 10A, 10B, and 10C schematically illustrate a configuration of thepiezoelectric element 330 illustrated in FIGS. 9A and 9B. FIGS. 10A and10C illustrate front and back surfaces of the piezoelectric element 330.FIG. 10B illustrates a side surface of the piezoelectric element 330.Each piezoelectric element 330 includes a piezoelectric member 331, afirst electrode 332, and a second electrode 333, as illustrated in FIG.9A. The first electrode 332 and the second electrode 333, being in anopposed relationship, are disposed on a plate surface of thepiezoelectric member 331. As described with reference to FIGS. 9A and9B, each piezoelectric element 330 can be configured as the multilayeredpiezoelectric element according to the present invention. In this case,it is feasible to give a driving waveform different in phase for eachpiezoelectric material layer when the piezoelectric member 331 isconfigured to have a structure including piezoelectric material layersand internal electrodes that are alternately disposed and when theinternal electrodes are alternately connected to the first electrode 332or the second electrode 333. In FIG. 10C, the surface on which the firstelectrode 332 is provided and is positioned on the front side of thepiezoelectric element 330 is referred to as a first electrode surface336. In FIG. 10A, the surface on which the second electrode 333 isprovided and is positioned on the front side of the piezoelectricelement 330 is referred to as a second electrode surface 337.

The electrode surface according to the present invention is a surface ofthe piezoelectric element on which the electrode is provided. Forexample, the first electrode 332 can be configured to have a wraparoundshape so that a part of the first electrode 332 is provided on thesecond electrode surface 337, as illustrated in FIG. 10B.

A plate surface of the vibration plate 320 is fixed to the firstelectrode surface 336 of the piezoelectric element 330, as illustratedin FIGS. 9A and 9B. When the piezoelectric element 330 is driven, astress generating between the piezoelectric element 330 and thevibration plate 320 induces an out-of-plane vibration of the vibrationplate 320. The dust removing apparatus 310 according to the presentinvention is an apparatus that can remove foreign substances, such asdust particles adhering to the surface of the vibration plate 320, byusing the out-of-plane vibration of the vibration plate 320. Theout-of-plane vibration is an elastic vibration that causes adisplacement of the vibration plate in the optical axis direction (i.e.,the thickness direction of the vibration plate).

FIGS. 11A and 11B are schematic diagrams illustrating a principle ofvibrations occurring in the dust removing apparatus 310 according to thepresent invention. FIG. 11A illustrates an out-of-plane vibration of thevibration plate 320 generated when alternating voltages having the samephase are applied to the pair of right and left piezoelectric elements330. The polarization direction of a piezoelectric material thatconstitutes each of the right and left piezoelectric elements 330 isidentical to the thickness direction of the piezoelectric element 330.The dust removing apparatus 310 is driving in a seventh vibration mode.FIG. 11B illustrates an out-of-plane vibration of the vibration plate320 generated when alternating voltages having mutually opposite phases(180° different) are applied to the pair of right and left piezoelectricelements 330. In this case, the dust removing apparatus 310 is drivingin a sixth vibration mode. The dust removing apparatus 310 according tothe present invention can effectively remove dust particles adhering tothe surface of the vibration plate by selectively operating in at leasttwo vibration modes.

<Imaging Apparatus>

Next, an imaging apparatus according to the present invention isdescribed in detail below. The imaging apparatus according to thepresent invention includes the above-mentioned dust removing apparatusand an image sensor unit, and is characterized in that the vibrationplate of the dust removing apparatus is provided on a light-receivingsurface of the image sensor unit. FIGS. 12 and 13 illustrate a digitalsingle lens reflex camera, which is an example of the imaging apparatusaccording to an example of the present invention.

FIG. 12 is a perspective view illustrating the front side of a camerabody 601, which can be seen from the imaging target side in a statewhere an imaging lens unit is removed. FIG. 13 is an explodedperspective view illustrating a schematic configuration of the camerainterior, in which the dust removing apparatus according to the presentinvention and a peripheral structure of the imaging unit 400 aredescribed in detail.

After having passed through the imaging lens unit, an imaging luminousflux can be guided into a mirror box 605 provided in the camera body601. A main mirror (e.g., a quick return mirror) 606 is disposed in themirror box 605. The main mirror 606 can be held at an inclined angle(e.g., 45°) relative to an imaging optical axis to guide the imagingluminous flux toward a penta-Dach mirror (not illustrated) or can beheld at a retreat position to guide the imaging luminous flux toward animage sensor (not illustrated).

The mirror box 605 and a shutter unit 200 are sequentially disposed onan imaging target side of a main body chassis 300 (i.e., a framework ofthe camera body). Further, the imaging unit 400 is disposed on aphotographer side of the main body chassis 300. The imaging unit 400 isadjusted and placed in such a way that an imaging surface of the imagesensor is spaced a predetermined distance from and positioned inparallel with a locating plane of a mount 602 to which the imaging lensunit is attached.

The imaging apparatus according to the present invention is not limitedto the above-mentioned digital single lens reflex camera and can beconfigured as a mirrorless digital single-lens reflex camera that doesnot include the mirror box 605 or any other imaging lens unitinterchangeable camera. Further, the imaging apparatus according to thepresent invention can be configured as an imaging lens unitinterchangeable video camera or another imaging apparatus, such as acopy machine, a facsimile machine, or a scanner. The imaging apparatusaccording to the present invention can be applied to any otherelectrical and electronic device that requires removal of dust particlesadhering to a surface of an optical component.

<Electronic Device>

Next, an electronic device according to the present invention isdescribed in detail below. The electronic device according to thepresent invention is characterized by a piezoelectric acoustic devicethat includes the piezoelectric element or the multilayeredpiezoelectric element. The piezoelectric acoustic device is, forexample, a speaker, a buzzer, a microphone, a surface acoustic wave(SAW) element.

FIG. 14 is an overall perspective view illustrating a main body 931 of adigital camera, which is seen from the front side thereof, as an exampleof the electronic device according to an example of the presentinvention. An optical apparatus 901, a microphone 914, a flash lightingunit 909, and an auxiliary light unit 916 are disposed on a frontsurface of the main body 931. The microphone 914 is mostly incorporatedin the main body 931. Therefore, the microphone 914 is indicated by adotted line. To pick up ambient sounds, the front part of the microphone914 is configured to have a through-hole shape.

A power button 933, a speaker 912, a zoom lever 932, and release button908 operable to perform an in-focus operation are disposed on an uppersurface of the main body 931. The speaker 912 is incorporated in themain body 931 and therefore indicated by a dotted line. An aperture isprovided on the front side of the speaker 912 to output sounds.

The piezoelectric acoustic device according to the present invention canbe provided in at least one of the microphone 914, the speaker 912, anda surface acoustic wave element.

The electronic device according to the present invention is not limitedto the above-mentioned digital camera. For example, the electronicdevice according to the present invention can be configured as a soundreproduction device, a voice recording device, a mobile phone, aninformation terminal, or any other electronic device that incorporates apiezoelectric acoustic device.

As mentioned above, the piezoelectric element and the multilayeredpiezoelectric element according to the present invention can bepreferably incorporated in a liquid discharge head, a liquid dischargeapparatus, an ultrasonic motor, an optical device, a vibratingapparatus, a dust removing apparatus, an imaging apparatus, and anelectronic device. Using the piezoelectric element and the multilayeredpiezoelectric element according to the present invention enables theprovision of a liquid discharge head that is comparable to or superiorto a referential liquid discharge head using a lead-containingpiezoelectric element in nozzle density and discharge speed.

Using the liquid discharge head according to the present inventionenables the provision of a liquid discharge apparatus that is comparableto or superior to a referential liquid discharge apparatus using alead-containing piezoelectric element in discharge speed and dischargeaccuracy.

Using the piezoelectric element and the multilayered piezoelectricelement according to the present invention enables the provision of anultrasonic motor that is comparable to or superior to a referentialultrasonic motor using a lead-containing piezoelectric element indriving force and durability.

Using the ultrasonic motor according to the present invention enablesthe provision of an optical device that is comparable to or superior toa referential optical device using a lead-containing piezoelectricelement in durability and operation accuracy.

Using the piezoelectric element and the multilayered piezoelectricelement according to the present invention enables the provision of avibrating apparatus that is comparable to or superior to a referentialvibrating apparatus using a lead-containing piezoelectric element invibration ability and durability.

Using the vibrating apparatus according to the present invention enablesthe provision of a dust removing apparatus that is comparable to orsuperior to a referential dust removing apparatus that uses alead-containing piezoelectric element in dust removing efficiency anddurability.

Using the dust removing apparatus according to the present inventionenables the provision of an imaging apparatus that is comparable to orsuperior to a referential imaging apparatus using a lead-containingpiezoelectric element in dust removing function.

Using the piezoelectric acoustic device including the piezoelectricelement or the multilayered piezoelectric element according to thepresent invention enables the provision of an electronic device that iscomparable to or superior to a referential electronic device using alead-containing piezoelectric element in sound generation.

The piezoelectric material according to the present invention can beincorporated in an ultrasonic oscillator, a piezoelectric actuator, apiezoelectric sensor, and a ferroelectric memory in addition to theabove-mentioned devices (e.g., the liquid discharge head and the motor).

Hereinafter, the present invention is described with reference tovarious examples. However, the present invention is not limited to thefollowing description of the examples.

The following is a description of actually fabricated examples of thepiezoelectric ceramics according to the present invention.

Examples 1 to 52, 76 to 80 and Comparative Examples 1 to 19

The raw material powder used to fabricate the piezoelectric ceramics hasan average grain diameter of 100 nm and includes, as main components,barium titanate (BaTiO₃, Ba/Ti=0.9985), calcium titanate (CaTiO₃,Ca/Ti=0.9978), calcium zirconate (CaZrO₃, Ca/Zr=0.999), and calciumstannate (CaSnO₃, Ca/Sn=1.0137). Further, the raw material powderincludes barium oxalate to adjust the value “a” indicating the ratio ofthe total mole number of Ba and Ca to the total mole number of Ti, Zr,and Sn. The weighing of the raw material powders of the above-mentionedmain components has been performed for each test piece in such a way asto attain the ratio illustrated in a table 1 when on a metal basis. Theweighing of tetramanganese trioxide, lithium carbonate, and bismuthoxide has been performed for each test piece in such a manner that thecontents of Mn (i.e., the first subcomponent), Li (i.e., the secondsubcomponent), and Bi (the third subcomponent), on a metal basis, attainthe ratio illustrated in the table when the main component metal oxideis 100 parts by weight. The above-mentioned weighed powder has beenmixed in a ball mill, by dry mixing, for 24 hours. To granulate theobtained mixed powder, a spray-dryer has been used to cause a PVAbinder, which is 3 parts by weight of the mixed powder, to adhere to asurface of the mixed powder. The test pieces of the examples 37 to 40and the example 76 have been mixed with magnesium oxide so that the Mgweight on a metal basis becomes 0.0049, 0.0099, 0.0499, 0.0999 and0.4999 parts by weight, respectively.

Next, a disk-shaped compact has been fabricated by using a press formingmachine that applies a compacting pressure of 200 MPa to a mold filledwith the above-mentioned granulated powder. It is useful to furtherpress the fabricated compact, for example, by using a cold isostaticpressing machine.

Then, the above-mentioned compact has been placed in the electricfurnace and held at the maximum temperature in a range of 1300 to 1380°C. for five hours. The compact has been sintered in the atmosphere for24 hours. Through the above-mentioned processes, a ceramics made of thepiezoelectric material according to the present invention has beenobtained.

Then, crystal grains that constitute the obtained ceramics have beenevaluated with respect to an average equivalent circle diameter andrelative density. As a result of the evaluation, it has been confirmedthat the average equivalent circle diameter is in a range from 10 to 50μm and the relative density of each test piece (except for thecomparative example 7) is equal to or greater than 95%. The polarizingmicroscope has been mainly used to observe the crystal grains. Further,the scanning electron microscope (SEM) has been used to specify thegrain diameter when the crystal grain is small. An observation resulthas been used to calculate the average equivalent circle diameter.Further, the relative density has been evaluated by using a latticeconstant obtained by the X-ray diffraction, a theoretical densitycalculated based on the weighed composition, and an actual densitymeasured according to the Archimedes method.

The test pieces of the examples 15 and 17 have been evaluated withrespect to valence of Mn. The temperature dependency in the magneticsusceptibility has been measured by the SQUID in a range from 2 to 60K.It has been confirmed that the average valence of Mn obtained based onthe temperature dependency in the magnetic susceptibility is +3.8 and3.9 in the examples 15 and 17, respectively. The tendency that thevalence of Mn decreases with increasing molar ratio of Bi to Mn has beenconfirmed. Further, it has been confirmed in the comparative example 19(i.e., the test piece not containing Bi) that the magneticsusceptibility of Mn is +4.0, when evaluated according to the similarmethod. More specifically, because the piezoelectric material accordingto the present invention includes Bi (i.e., the third subcomponent) insuch a way as to reduce the valence of Mn (i.e., the firstsubcomponent), the ability of the piezoelectric material serving as theacceptor of Mn can be promoted. As a result, the mechanical qualityfactor of the piezoelectric material according to the present inventionbecomes higher.

Next, the composition of the obtained ceramics has been evaluated basedon ICP emission spectrophotometric analysis. It has been confirmed inall piezoelectric materials that the composition after sinteringcoincides with the composition after weighing with respect to Ba, Ca,Ti, Zr, Sn, Mn, Li and Bi. Further, in the examples 1 to 36 and 41 to 52and the comparative examples 1 to 14 and 16 to 19, it has been confirmedthat the content of Mg is 0.0001 parts by weight when the metal oxideexpressed using the chemical formula(Ba_(1-x)Ca_(x))_(a)(Ti_(1-y-z)Zr_(y)Sn_(z))O₃ is 100 parts by weight.On the other hand, in the examples 37 to 40, it has been confirmed thatthe content of Mg is 0.0050, 0.0100, 0.0500, and 0.1000 parts by weight,respectively. In the example 76, it has been confirmed that the contentof Mg is 0.5000 parts by weight.

Next, the obtained ceramics has been polished to have a thickness of 0.5mm and the crystal structure has been analyzed based on X-raydiffraction. As a result, only the peak corresponding to the perovskitestructure has been observed in all test pieces except for thecomparative example 1.

Then, gold electrodes each having a thickness of 400 nm have been formedon the front and back surfaces of the disk-shaped ceramics according toa DC sputtering method. In addition, a titanium film having a thicknessof 30 nm has been formed to provide an adhesion layer between eachelectrode and the ceramics. Then, the electrode equipped ceramics hasbeen cut into a strip-form piezoelectric element having a size of 10mm×2.5 mm×0.5 mm. The fabricated piezoelectric element has been placedon a hot plate whose surface temperature increases from 60° C. to 100°C. The piezoelectric element placed on the hot plate has been subjectedto polarization processing under an application of an electric field of1 kV/mm for 30 minutes.

As static characteristics of a piezoelectric element that includes apiezoelectric material according to the present invention or apiezoelectric material according to a comparative example, thepiezoelectric constant d₃₁ and the mechanical quality factor Qm of thepiezoelectric element subjected to the polarization processing have beenevaluated according to the resonant-antiresonant method. In calculatingT_(ot), T_(to), and T_(C), an impedance analyzer (e.g., 4194Amanufactured by Agilent Techonologies Inc.) has been used to measure theelectric capacity while changing the temperature of respective testpieces. Simultaneously, the impedance analyzer has been used to measurethe temperature dependency in the dielectric tangent. The test piece hasbeen cooled until the temperature decreases to −100° C. from the roomtemperature and then heated until the temperature reaches 150° C. Thephase transition temperature T_(to) represents the temperature at whichthe crystal system changes from tetragonal to orthorhombic. The phasetransition temperature T_(to) has been defined as the temperature atwhich a derivative, which is obtainable by differentiating a dielectricconstant measured in the cooling process of the test piece by the testpiece temperature, can be maximized. T_(ot) represents the temperatureat which the crystal system changes from orthorhombic to tetragonal andhas been defined as the temperature at which a derivative, which isobtainable by differentiating the dielectric constant measured in theheating process of the test piece by the test piece temperature, can bemaximized. The Curie temperature T_(C) represents the temperature atwhich the dielectric constant can be maximized around the phasetransition temperature of the ferroelectric phase (tetragonal phase) andthe paraelectric phase (cubic phase). The Curie temperature T_(C) hasbeen defined as the temperature at which the dielectric constant valuemeasured in the heating process of the test piece becomes a maximalvalue.

TABLE 1 First Second Third Subcomponent Subcomponent Subcomponent MainComponent Mn Li Bi Sintering Ba Ca Ti Zr Sn Parts By Parts By Parts ByTemperature 1 − x x 1 − y − z y z a Weight Weight Weight (° C.)Comparative Example 1 0.680 0.320 0.950 0.050 0.000 0.9990 0.240 0.00060.170 1360 Example 1 0.700 0.300 0.915 0.085 0.000 0.9994 0.120 0.00060.170 1360 Example 2 0.700 0.300 0.931 0.069 0.000 0.9994 0.240 0.00060.170 1360 Example 3 0.700 0.300 0.950 0.050 0.000 0.9994 0.240 0.00060.170 1360 Example 4 0.700 0.300 0.959 0.041 0.000 0.9994 0.240 0.00060.170 1360 Example 5 0.720 0.280 0.925 0.075 0.000 0.9994 0.240 0.00060.170 1360 Example 6 0.740 0.260 0.955 0.045 0.000 0.9994 0.240 0.00060.170 1360 Example 7 0.740 0.260 0.938 0.062 0.000 0.9994 0.240 0.00060.170 1360 Example 8 0.740 0.260 0.955 0.045 0.000 0.9994 0.240 0.00060.170 1360 Example 9 0.780 0.220 0.935 0.065 0.000 0.9994 0.240 0.00060.170 1360 Example 10 0.800 0.200 0.945 0.055 0.000 0.9994 0.240 0.00060.170 1360 Example 11 0.813 0.187 0.940 0.060 0.000 0.9994 0.240 0.00060.170 1360 Example 12 0.813 0.187 0.940 0.040 0.020 0.9994 0.240 0.00060.170 1360 Comparative Example 2 0.830 0.170 0.935 0.065 0.000 1.00310.180 0.0008 0.025 1340 Example 13 0.830 0.170 0.935 0.055 0.010 0.99710.180 0.0006 0.170 1340 Example 14 0.830 0.170 0.935 0.045 0.020 0.99710.180 0.0006 0.170 1340 Example 15 0.830 0.170 0.935 0.065 0.000 0.99710.180 0.0006 0.170 1340 Comparative Example 3 0.830 0.170 0.935 0.0650.000 1.0031 0.360 0.0008 0.025 1340 Example 16 0.830 0.170 0.935 0.0550.010 1.0042 0.360 0.0006 0.170 1340 Example 17 0.830 0.170 0.935 0.0650.000 1.0042 0.360 0.0006 0.170 1340 Comparative Example 4 0.840 0.1600.950 0.050 0.000 1.0031 0.180 0.0008 0.025 1340 Example 18 0.840 0.1600.950 0.040 0.010 0.9971 0.180 0.0006 0.170 1340 Example 19 0.840 0.1600.950 0.050 0.000 0.9971 0.180 0.0006 0.170 1340 Comparative Example 50.840 0.160 0.950 0.050 0.000 1.0100 0.360 0.0008 0.025 1340 Example 200.840 0.160 0.950 0.040 0.010 1.0042 0.360 0.0006 0.170 1340 Example 210.840 0.160 0.950 0.050 0.000 1.0042 0.360 0.0006 0.170 1340 Example 220.845 0.155 0.931 0.069 0.000 0.9994 0.240 0.0006 0.170 1340 Example 230.860 0.140 0.930 0.070 0.000 0.9955 0.160 0.0000 0.181 1320 ComparativeExample 6 0.870 0.130 0.941 0.059 0.000 1.0055 0.240 0.0008 0.025 1320Comparative Example 7 0.870 0.130 0.941 0.059 0.000 1.0210 0.240 0.00060.170 1320 Comparative Example 8 0.870 0.130 0.941 0.059 0.000 0.98500.240 0.0006 0.170 1320 Example 24 0.870 0.130 0.941 0.059 0.000 0.99940.240 0.0006 0.170 1320 Example 25 0.870 0.130 0.941 0.059 0.000 0.99940.240 0.0005 0.170 1320 Example 26 0.870 0.130 0.941 0.059 0.000 0.99940.240 0.0003 0.170 1320 Example 79 0.870 0.130 0.941 0.059 0.000 0.99940.240 0.0002 0.170 1320 Example 80 0.870 0.130 0.941 0.059 0.000 0.99940.240 0.0012 0.170 1320 Example 27 0.870 0.130 0.941 0.059 0.000 0.99940.240 0.0012 0.340 1320 Example 28 0.870 0.130 0.941 0.059 0.000 0.99940.240 0.0006 0.170 1350 Comparative Example 11 0.880 0.120 0.941 0.0590.000 1.0055 0.240 0.0009 0.025 1320 Example 29 0.880 0.120 0.941 0.0590.000 0.9994 0.240 0.0006 0.170 1320 Example 30 0.880 0.120 0.941 0.0590.000 0.9994 0.240 0.0012 0.340 1320 Example 31 0.880 0.120 0.941 0.0590.000 0.9994 0.240 0.0006 0.170 1350 Comparative Example 12 0.890 0.1100.941 0.059 0.000 1.0055 0.240 0.0009 0.025 1320 Example 32 0.890 0.1100.941 0.059 0.000 0.9994 0.240 0.0006 0.170 1350 Example 33 0.890 0.1100.941 0.059 0.000 0.9994 0.240 0.0006 0.170 1320 Example 34 0.890 0.1100.941 0.059 0.000 0.9994 0.240 0.0012 0.340 1320 Example 35 0.890 0.1100.941 0.059 0.000 0.9969 0.240 0.0012 0.510 1320 Comparative Example 130.890 0.110 0.980 0.020 0.000 0.9997 0.240 0.0006 0.170 1320 ComparativeExample 14 0.915 0.085 0.955 0.045 0.000 0.9998 0.240 0.0006 0.170 1320Example 36 0.890 0.110 0.941 0.059 0.000 0.9994 0.040 0.0006 0.850 1320Example 37 0.860 0.140 0.940 0.060 0.000 1.0004 0.160 0.0000 0.094 1340Example 38 0.860 0.140 0.940 0.060 0.000 1.0004 0.160 0.0000 0.094 1340Example 39 0.860 0.140 0.940 0.060 0.000 1.0004 0.160 0.0000 0.094 1340Example 40 0.860 0.140 0.940 0.060 0.000 1.0004 0.160 0.0000 0.094 1340Example 76 0.860 0.140 0.940 0.060 0.000 1.0004 0.160 0.0000 0.094 1340Example 41 0.860 0.140 0.940 0.060 0.000 1.0004 0.160 0.0000 0.094 1340Example 42 0.860 0.140 0.940 0.060 0.000 1.0004 0.160 0.0000 0.189 1340Example 43 0.860 0.140 0.940 0.060 0.000 1.0004 0.160 0.0000 0.239 1340Example 44 0.860 0.140 0.930 0.070 0.000 1.0004 0.160 0.0000 0.189 1320Example 45 0.860 0.140 0.930 0.070 0.000 1.0004 0.160 0.0000 0.189 1340Example 46 0.860 0.140 0.930 0.070 0.000 1.0004 0.160 0.0000 0.189 1380Example 47 0.860 0.140 0.915 0.085 0.000 1.0004 0.160 0.0000 0.539 1380Example 48 0.860 0.140 0.950 0.050 0.000 1.0004 0.140 0.0000 0.189 1340Example 49 0.860 0.140 0.920 0.080 0.000 1.0004 0.140 0.0000 0.289 1340Example 50 0.860 0.140 0.920 0.080 0.000 1.0004 0.140 0.0000 0.339 1340Example 51 0.830 0.170 0.925 0.075 0.000 0.9998 0.140 0.0000 0.189 1380Example 52 0.830 0.170 0.915 0.085 0.000 1.0010 0.120 0.0012 0.189 1300Example 77 0.890 0.110 0.970 0.025 0.000 1.0019 0.300 0.0008 0.250 1340Example 78 0.910 0.090 0.960 0.040 0.000 1.0019 0.300 0.0008 0.250 1340Comparative Example 16 0.830 0.170 0.905 0.095 0.000 1.0010 0.120 0.00100.189 1300 Comparative Example 17 0.830 0.170 0.920 0.050 0.030 1.00100.120 0.0012 0.189 1300 Comparative Example 18 1.000 0.000 1.000 0.0000.000 1.0000 0.023 0.0120 0.188 1320 Comparative Example 19 1.000 0.0001.000 0.000 0.000 1.0000 0.023 0.0000 0.000 1320

Table 2 summarizes properties of the test pieces according to theexamples and the comparative examples in the table 1 with respect topiezoelectric constant d₃₁, mechanical quality factor, dielectrictangent, T_(c), T_(to), and T_(ot) at the room temperature.

TABLE 2 Piezoelectric Mechanical Dielectric Constant Quality Tangentd31(pm/V) (—) (—) Tc(° C.) Tto(° C.) Tot(° C.) Comparative Example 1 521190 0.004 116 −79 −71 Example 1 121 810 0.001 102 −45 −38 Example 2 811120 0.003 108 −52 −46 Example 3 72 1190 0.004 116 −75 −68 Example 4 651230 0.002 120 −86 −78 Example 5 87 1090 0.005 106 −37 −29 Example 6 571210 0.002 118 −73 −66 Example 7 74 1150 0.002 111 −53 −47 Example 8 571220 0.002 118 −73 −66 Example 9 77 1140 0.004 110 −41 −33 Example 10 801180 0.006 114 −49 −41 Example 11 72 1160 0.010 112 −41 −34 Example 1275 1240 0.002 120 −55 −49 Comparative Example 2 89 740 0.002 110 −38 −31Example 13 85 1060 0.002 114 −44 −36 Example 14 83 1200 0.002 118 −51−43 Example 15 89 1000 0.002 110 −37 −30 Comparative Example 3 78 9500.003 110 −34 −28 Example 16 58 1400 0.002 114 −26 −19 Example 17 531380 0.002 110 −21 −13 Comparative Example 4 80 500 0.004 116 −68 −60Example 18 64 1120 0.006 120 −60 −53 Example 19 74 1080 0.010 116 −53−47 Comparative Example 5 38 860 0.002 116 −50 −43 Example 20 28 14800.002 120 −42 −34 Example 21 38 1440 0.002 116 −35 −27 Example 22 811120 0.003 108 −23 −16 Example 23 98 1300 0.001 108 −26 −20 ComparativeExample 6 87 780 0.003 110 −26 −16 Comparative Example 7 76 1160 0.002112 −30 −22 Comparative Example 8 72 1160 0.002 112 −30 −22 Example 2482 1160 0.004 112 −34 −24 Example 25 85 1160 0.006 112 −34 −28 Example26 83 1160 0.002 112 −35 −28 Example 79 72 1160 0.002 112 −30 −22Example 80 72 1160 0.002 112 −30 −22 Example 27 55 1540 0.003 112 −42−36 Example 28 72 1160 0.001 112 −30 −24 Comparative Example 11 87 5800.003 112 −18 −11 Example 29 72 1160 0.002 112 −28 −20 Example 30 551540 0.002 112 −32 −24 Example 31 72 1160 0.004 112 −28 −21 ComparativeExample 12 87 580 0.006 112 −12 −6 Example 32 72 1160 0.010 112 −26 −19Example 33 75 1110 0.002 112 −24 −16 Example 34 55 1540 0.002 112 −36−28 Example 35 38 920 0.002 112 −28 −21 Comparative Example 13 33 13200.002 128 −22 −16 Comparative Example 14 58 1220 0.002 118 −10 0 Example36 44 720 0.003 112 −22 −30 Example 37 97 690 0.002 112 −47 −39 Example38 98 690 0.002 112 −45 −38 Example 39 95 690 0.004 112 −47 −41 Example40 97 690 0.006 112 −46 −39 Example 76 94 560 0.010 106 −40 −32 Example41 97 690 0.002 112 −47 −39 Example 42 87 1070 0.002 112 −37 −30 Example43 82 1270 0.002 112 −32 −26 Example 44 99 1030 0.002 108 −25 −18Example 45 96 1080 0.002 108 −26 −18 Example 46 97 1070 0.002 108 −25−17 Example 47 109 880 0.003 102 −28 −21 Example 48 94 1070 0.002 104−24 −16 Example 49 104 1350 0.002 104 −20 −13 Example 50 103 1550 0.003104 −20 −12 Example 51 106 970 0.002 106 −27 −19 Example 52 104 8900.002 104 −21 −14 Example 77 55 970 0.004 120 −63 −50 Example 78 60 8700.003 108 −68 −60 Comparative Example 16 125 870 0.003 98 −11 −5Comparative Example 17 117 870 0.005 98 −16 −9 Comparative Example 18 55220 0.015 123 −16 0 Comparative Example 19 74 280 0.020 127 −4 16

The test piece of the comparative example 1 has a larger Ca amount “x”value (i.e., 0.320). In the measurement of X-ray diffraction, a CaTiO3phase (i.e., an impurity phase) has been detected. It has been confirmedthat the piezoelectric constant d₃₁ of the test piece is lower by 20μm/V compared to the test piece of the example 3 that is identical tothe comparative example 1 in the amounts of Ti, Zr, and Bi, although theCa amount “x” is 0.300.

The test piece of the comparative example 14 has a smaller Ca amount “x”value (i.e., 0.085). Therefore, the test piece of the comparativeexample 14 has a higher T_(to) value (i.e., −10° C.) and a higher T_(ot)value (i.e., 0° C.) It has been confirmed that the temperaturedependency in the piezoelectric constant is large in the operatingtemperature range.

The test piece of the comparative example 16 has a larger Zr amount “y”value (i.e., 0.095). Therefore, the T_(c) value is relatively lower(i.e., 98° C.), the Tto value is higher (−11° C.), and the Tot value ishigher (−5° C.). On the contrary, in the test piece of the example 52(y=0.085) that is identical to the test piece of the comparative example16 in the Ca amount, it has been confirmed that the Tc value is 104° C.,the Tto value is −21° C., and the Tot value is −14° C.

The test piece of the comparative example 13 has a smaller Zr amount “y”value (i.e., 0.020). It has been confirmed that the piezoelectricconstant d₃₁ of the test piece is lower by 42 μm/V compared to theexample 33 (y=0.059) that is identical to the comparative example 13 inthe Ca amount.

The test piece of the comparative example 8 has a smaller “a” value(i.e., 0.985) and therefore an abnormal grain growth has been observed.The material strength may be insufficient in cut working and polishworking because the particle diameter is greater than 50 μm. Inaddition, it has been confirmed that the piezoelectric constant d₃₁ ofthe test piece is lower by 10 μm/V compared to the example 24.

The test piece of the example 14 contains Ti although a part of Ti isreplaced by Zr and Sn. The test piece of the example 14 has demonstratedsatisfactory characteristics, which include a higher Qm value (by anamount of 460), a lower T_(to) value (by an amount of 13° C.), and alower T_(ot) value (by an amount of 12° C.) compared to the comparativeexample 2 (y=0.065, Z=0.000) that is identical to the example 14 in theTi amount.

The test piece of the comparative example 17 has a larger Sn amount “z”(i.e., 0.03). It has been confirmed that the Tc value of the test pieceis 98° C. In other word, the test piece of the comparative example 17has a lower Tc value (by an amount of 6° C.) compared to the example 52(y=0.082, z=0.003) that is identical to the comparative example 17 inthe Ti amount.

Further, if the phase transition temperature is evaluated on thecomparative examples 6, 11, and 12 and the examples 24, 27, 29, 30, 33,and 34 in the table 2, it is understood that adding the Bi component iseffective to reduce the T_(to) value and the T_(ot) value withoutreducing the Curie temperature T_(c) of the piezoelectric material. Morespecifically, it has been confirmed that a sample of each example has asmaller temperature dependency in the piezoelectric characteristicscompared to a comparable sample that is similar in the Tc amount.

Next, to confirm the durability of the piezoelectric element, testpieces of the examples 24, 27, 29, 30, 33, and 34 and the comparativeexamples 11 and 12 have been placed in a thermostat chamber andsubjected to a temperature cycle test. The temperature cycle testincludes 100 cycles repetitively performed, in each cycle of which thetemperature changes in order of 25° C.→−20° C.→50° C.→25° C. Thepiezoelectric constant d₃₁ values have been compared before and afterthe cycle test. The test pieces of the examples 24, 27, 29, 30, 33, and34, in which the phase transition temperature T_(to) is −20 or less,have demonstrated that a change rate in piezoelectric characteristics is5% or less. On the other hand, test pieces of the comparative examples11 and 12 whose phase transition temperature T_(to) is higher than −20°C. have demonstrated that a reduction amount of the piezoelectricconstant d₃₁ is greater than 5%. In the comparative example 6, the phasetransition temperature T_(to) of the test piece is equal to or less than−20° C. The change rate in the piezoelectric constant d₃₁ after thecycle test is equal to or less than 5%. However, the mechanical qualityfactor at the room temperature is lower (by an amount of 380) comparedto the example 24.

The test piece whose phase transition temperature T_(to) is higher than−20° C. causes repetitive phase transitions between tetragonal andorthorhombic during the temperature cycle test. Causing repetitive phasetransitions between crystal systems that are different in spontaneouspolarization direction can promote depolarization. It is believed thatthe reduced amount of the piezoelectric constant d₃₁ is larger in thetest piece whose phase transition temperature T_(to) is higher than −20°C. More specifically, the piezoelectric ceramics can be evaluated asbeing dissatisfactory in element durability if the phase transitiontemperature T_(t0) is high than −20° C.

To confirm adhesion properties of the electrode of each piezoelectricelement, a grid-pattern tape test (former JIS K5400) has been conductedon the test pieces of the examples 24, 27, 29, 30, 33, and 34. Theconducted grid-pattern tape test includes forming eleven parallelnotches at intervals of 2 mm, using a utility knife, in such a way as tohave the depth reaching the body underlying the electrode and thenforming similar notches on the electrode after the test piece is rotatedby an angle of 90 degrees. The conducted grid-pattern tape test furtherincludes strongly putting an adhesive tape on the grid-pattern portionof the electrode and then immediately peeling the tape off the electrodewhile holding an edge of the tape at the angle of 45 degrees. As aresult of the above-mentioned test, it has been confirmed that thenumber of peeled square electrodes is equal to or less than 5% of allsquare electrodes divided into the size of 2 mm×2 mm.

The test piece of the example 76 (in which the content of Mg exceeds0.1000 parts by weight) has a relatively lower mechanical qualityfactor, compared to the examples 37 to 41 in which the Mg amount is in arange from 0.005 parts by weight to 0.1000 parts by weight.

Further, the piezoelectric materials of the examples 47, and 49 to 52(in which the Zr amount exceeds 0.074) have demonstrated excellentpiezoelectric characteristics, especially in that the piezoelectricconstant exceeds 100 μm/V.

Further, it has been confirmed that the mechanical quality factor isremarkably lower (namely, less than 300) in the comparative examples 18and 19.

FIGS. 15A to 18D illustrate temperature dependencies of the test piecesin the comparative examples 2 to 5 and the examples 15, 17, 18, and 21in the table 1 with respect to relative dielectric constant, dielectrictangent, piezoelectric constant d₃₁, and mechanical quality factor. Itis understood from FIGS. 15A to 15D that a sample containing the Bicomponent has a phase transition temperature shifted toward a lowtemperature side and a relative dielectric constant having a smallerchange width in a measurement temperature range, compared to a samplecontaining not Bi component. Further, it is understood from FIG. 16A to16D that the dielectric tangent can be remarkably reduced at −20° C. orless in the sample of the example 15 that contains a sufficient amountof Bi. It is understood from FIG. 17A to 17D that adding the Bicomponent is effective to decrease a change width of the piezoelectricconstant d₃₁ in the measurement temperature range. It is understood fromFIG. 18A to 18D that adding the Bi component is effective to increasethe mechanical quality factor in the measurement temperature range.

<Examples 53 to 60 and Comparative Examples 20 to 23>

The raw material powder used to fabricate the piezoelectric ceramics hasan average grain diameter of 100 nm and includes barium titanate,calcium titanate, calcium zirconate, lithium carbonate, bismuth oxide,and tetramanganese trioxide, in addition to glass assistant containingSi and B (including SiO₂ by 30 to 50 wt. %, and B₂O₃ by 21.1 wt. %). Theweighing of the above-mentioned raw material powder has been performedfor each test piece in such a way as to realize the ratio indicated intable 3. Subsequently, a compact has been fabricated using a methodsimilar to that used for the test pieces described in the table 1. Theobtained compact has been held in an electric furnace held at 1200° C.for five hours and sintered in the atmosphere for 24 hours.Subsequently, each test piece has been subjected to working andevaluation similar to those applied to the test pieces described in thetable 1.

TABLE 3 Fifth First Second Third Subcomponent Subcomponent SubcomponentSubcomponent Glass Main Component Mn Li Bi Assistant Sintering Ba Ca TiZr Sn Parts By Parts By Parts By Parts By Temperature 1 − x x 1 − y − zy z a Weight Weight Weight Weight (° C.) Comparative 0.870 0.130 0.9700.030 0.000 1.0079 0.300 0.0008 0.025 0.100 200 Example 20 Example 530.870 0.130 0.970 0.030 0.000 1.0019 0.300 0.0003 0.084 0.100 200Example 54 0.870 0.130 0.970 0.030 0.000 1.0019 0.300 0.0006 0.170 0.100200 Comparative 0.870 0.130 0.970 0.030 0.000 0.9900 0.000 0.0006 0.1700.100 200 Example 21 Comparative 0.870 0.130 0.970 0.030 0.000 1.00600.400 0.0006 0.170 0.100 200 Example 22 Example 55 0.870 0.130 0.9700.030 0.000 1.0019 0.300 0.0008 0.250 0.100 200 Example 56 0.870 0.1300.970 0.030 0.000 0.9968 0.300 0.0012 0.840 0.100 200 Comparative 0.8700.130 0.970 0.030 0.000 0.9968 0.300 0.0012 1.690 0.100 200 Example 23Example 57 0.880 0.120 0.960 0.040 0.000 1.0019 0.300 0.0008 0.250 0.100200 Example 58 0.890 0.110 0.970 0.025 0.000 1.0019 0.300 0.0008 0.2500.100 200 Example 59 0.900 0.100 0.970 0.030 0.000 1.0019 0.300 0.00080.250 0.100 200 Example 60 0.910 0.090 0.960 0.040 0.000 1.0019 0.3000.0008 0.250 0.100 200

The following table 4 summarizes measurement results of the examples andthe comparative examples described in table 3 at the room temperaturewith respect to electromechanical coupling factor k₃₁, Young's modulusY₁₁, piezoelectric constant d₃₁, mechanical quality factor Qm, relativedielectric constant ∈_(r), T_(to), T_(ot), and T_(c).

TABLE 4 Electro- Mechanical Relative Di- Li Bi mechanical Young'sPiezoelectric Quality Dielectric electric Parts By Parts By CouplingModulus Constant Factor Constant Tangent Tto Tot Tc Weight Weight FactorY₁₁ (GPa) d₃₁ (pm/V) Qm (—) ∈ r (—) (—) (° C.) (° C.) (° C.) Comparative0.0008 0.025 0.228 121 72 669 1347 0.004 −42 −30 116 Example 20 Example53 0.0003 0.084 0.221 119 68 746 1300 0.004 −44 −32 118 Example 540.0006 0.170 0.218 120 66 923 1283 0.005 −46 −37 116 Comparative 0.00060.170 0.216 121 65 723 1274 0.003 −46 −37 118 Example 21 Comparative0.0006 0.170 0.213 123 66 743 1263 0.014 −46 −39 120 Example 22 Example55 0.0008 0.250 0.217 121 68 834 1276 0.003 −53 −46 116 Example 560.0012 0.840 0.218 124 63 1120 1132 0.004 −59 −53 118 Comparative 0.00121.690 0.153 119 43 1108 931 0.002 <−100 <−100 120 Example 23 Example 570.0003 0.084 0.215 126 62 909 1198 0.001 −55 −40 118 Example 58 0.00060.170 0.207 131 56 973 1101 0.004 −65 −55 120 Example 59 0.0008 0.2500.197 134 52 1044 1037 0.005 −70 −65 116 Example 60 0.0012 0.840 0.159144 64 876 876 0.003 −68 −60 112

The test piece of the comparative example 21 does not contain any Mncomponent. It has been confirmed that the mechanical quality factor Qmof the test piece of the comparative example 21 is lower (at least 200)than that of the test piece of the example 54.

It has been confirmed in a sample of the comparative example 22, whichincludes Mn by 0.36 parts by weight or more, that the dielectric tangentexceeds 0.01 and becomes higher than the dielectric tangent (i.e.,0.005) of the example 54.

The comparative example 20 has demonstrated the lowest mechanicalquality factor because the addition amount of the Bi component is lessthan 0.042 parts by weight.

The comparative example 23 has demonstrated a lower value with respectto the piezoelectric constant d₃₁ (approximately lower by 20) comparedto the example 56, because the addition amount of the Bi component isgreater than 0.858 parts by weight.

Example 61

The weighing of barium titanate (BaTiO₃), calcium titanate (CaTiO₃),calcium zirconate (CaZrO₃), lithium carbonate (Li₂CO₃), bismuth oxide(Bi₂O₃), tetramanganese trioxide (Mn₃O₄), and glass assistant containingSi and B (including SiO₂ by 30 to 50 wt. % and B₂O₃ by 21.1 wt. %) hasbeen performed for a test piece in such a way as to attain thecomposition of the example 54 described in the table 3. The weighed rawmaterial powder has been mixed in the ball mill for a night to obtain amixed powder.

Then, the obtained mixed powder has been mixed with an additive of PVBand formed into a green sheet having a thickness of 50 μm according to adoctor blade method.

Then, to form an internal electrode, an electrically conductive pastehas been printed on the above-mentioned green sheet. The electricallyconductive paste used in this case is an alloy paste containing Ag60%-Pd 40%. Then, a multilayered body has been obtained by successivelystacking nine green sheets with the electrically conductive pasteapplied thereon. Then, a sintered compact has been obtained by sinteringthe above-mentioned multilayered body at 1200° C. for five hours. Thesintered compact has been cut into a piece having a size of mm×2.5 mm.Subsequently, side surfaces of the sintered compact have been polishedand a pair of external electrodes (i.e., the first electrode and thesecond electrode), each electrically connecting the internal electrodesalternately, has been formed by Au sputtering. Through theabove-mentioned processes, the multilayered piezoelectric elementillustrated in FIG. 2B has been fabricated.

The observation on the internal electrodes of the obtained multilayeredpiezoelectric element has revealed that Ag—Pd (i.e., the electrodematerial) layers and piezoelectric material layers are alternatelyformed.

Prior to the evaluation of piezoelectricity, the test piece has beensubjected to polarization processing. More specifically, the test piecehas been heated in an oil bath at 100° C. A voltage of 1 kV/mm has beenapplied between the first electrode and the second electrode for 30minutes. Then, under continuous application of the voltage, the testpiece has been cooled until the temperature reaches the roomtemperature.

According to the evaluation of the piezoelectricity, it has beenconfirmed that the obtained multilayered piezoelectric element possessessufficient insulating properties and also possesses satisfactorypiezoelectric characteristics comparable to the piezoelectric materialof the example 33.

Example 62

A mixed powder has been fabricated by using a method similar to that ofthe example 61. Then, a calcined powder has been obtained by performingcalcination in the atmosphere at 1000° C. for three hours while rotatingthe obtained mixed powder in a rotary kiln. Then, the obtained calcinedpowder has been cracked in the ball mill. Then, the obtained crackedpowder has been mixed with an additive of PVB and formed into a greensheet having a thickness of 50 μm according to the doctor blade method.Then, to form an internal electrode, an electrically conductive pastehas been printed on the above-mentioned green sheet. The electricallyconductive paste used in this case is a Ni paste. Then, a multilayeredbody has been obtained by successively stacking nine green sheets withthe electrically conductive paste applied thereon. Then, the obtainedmultilayered body has been subjected to thermocompression bonding.

Further, the thermocompression-bonded multilayered body has beensintered in a tube furnace. The sintering has been performed in theatmosphere until the temperature increases to 300° C. Then, after beingsubjected to debinding, the sintered multilayered body has been placedin a reducing atmosphere (H₂:N₂=2:98, oxygen concentration 2×10⁻⁶ Pa)and held at 1200° C. for five hours. In a temperature-fall processreaching the room temperature, the oxygen concentration has beenswitched to 30 Pa at 1000° C. or less.

Then, the sintered compact obtained in the above-mentioned manner hasbeen cut into a piece having a size of mm×2.5 mm. Subsequently, sidesurfaces of the sintered compact have been polished and a pair ofexternal electrodes (i.e., the first electrode and the secondelectrode), each electrically connecting the internal electrodesalternately, has been formed by Au sputtering. Through theabove-mentioned processes, the multilayered piezoelectric elementillustrated in FIG. 2B has been fabricated.

The observation on the internal electrodes of the obtained multilayeredpiezoelectric element has revealed that Ni (i.e., the electrodematerial) layers and piezoelectric material layers are alternatelyformed. The obtained multilayered piezoelectric element has beensubjected to polarization processing in the oil bath at 100° C. underapplication of the electric field of 1 kV/mm for 30 minutes. Accordingto the evaluation of piezoelectric characteristics on the obtainedmultilayered piezoelectric element, it has been confirmed that theobtained multilayered piezoelectric element possesses sufficientinsulating properties and also possesses satisfactory piezoelectriccharacteristics comparable to the piezoelectric element of the example54.

Example 63

The piezoelectric element of the example 20 has been used to fabricatethe liquid discharge head illustrated in FIG. 3. It has been confirmedthat the fabricated liquid discharge head can discharge an ink accordingto an input electric signal.

Example 64

The liquid discharge head of the example 63 has been used to fabricatethe liquid discharge apparatus illustrated in FIG. 4. It has beenconfirmed that the fabricated liquid discharge apparatus can dischargean ink to a recording medium according to an input electric signal.

Example 65

The piezoelectric element of the example 20 has been used to fabricatethe ultrasonic motor illustrated in FIG. 6A. It has been confirmed thatthe fabricated ultrasonic motor can rotate according to an appliedalternating voltage.

Example 66

The ultrasonic motor of the example 65 has been used to fabricate theoptical device illustrated in FIG. 7. It has been confirmed that thefabricated optical device can perform an auto-focusing operationaccording to an applied alternating voltage.

Example 67

The piezoelectric element of the example 20 has been used to fabricatethe dust removing apparatus illustrated in FIG. 9. It has been confirmedthat the fabricated dust removing apparatus can attain satisfactory dustremoval efficiency in the event of spraying plastic beads underapplication of an alternating voltage.

Example 68

The dust removing apparatus of the example 67 has been used to fabricatethe imaging apparatus illustrated in FIG. 12. It has been confirmed thatthe fabricated imaging apparatus can adequately remove dust particlesfrom a surface thereof when the imaging unit is in an operating mode andcan obtain an image free from dust defect.

Example 69

The multilayered piezoelectric element of the example 61 has been usedto fabricate the liquid discharge head illustrated in FIG. 3. It hasbeen confirmed that the fabricated liquid discharge head can dischargean ink according to an input electric signal.

Example 70

The liquid discharge head of the example 69 has been used to fabricatethe liquid discharge apparatus illustrated in FIG. 4. It has beenconfirmed that the fabricated liquid discharge apparatus can dischargean ink to a recording medium according to an input electric signal.

Example 71

The multilayered piezoelectric element of the example 61 has been usedto fabricate the ultrasonic motor illustrated in FIG. 6B. It has beenconfirmed that the fabricated ultrasonic motor can rotate according toan applied alternating voltage.

Example 72

The ultrasonic motor of the example 71 has been used to fabricate theoptical device illustrated in FIG. 7. It has been confirmed that thefabricated optical device can perform an auto-focusing operationaccording to an applied alternating voltage.

Example 73

The multilayered piezoelectric element of the example 61 has been usedto fabricate the dust removing apparatus illustrated in FIG. 9. It hasbeen confirmed that the fabricated dust removing apparatus can attainsatisfactory dust removal efficiency in the event of spraying plasticbeads under application of an alternating voltage.

Example 74

The dust removing apparatus of the example 67 has been used to fabricatethe imaging apparatus illustrated in FIG. 12. It has been confirmed thatthe fabricated imaging apparatus can adequately remove dust particlesfrom a surface thereof when the imaging unit is an operating mode andcan obtain an image free from dust defect.

Example 75

The multilayered piezoelectric element of the example 61 has been usedto fabricate the electronic device illustrated in FIG. 14. It has beenconfirmed that the fabricated electronic device can perform a speakeroperation according to an applied alternating voltage.

The piezoelectric material according to the present invention possessessatisfactory piezoelectricity even in a high-temperature environment.Further, the piezoelectric material according to the present inventiondoes not contain any lead component and therefore can reduce anenvironmental load. The piezoelectric material according to the presentinvention can be preferably used for various devices, such as a liquiddischarge head, an ultrasonic motor, and a dust removing apparatus, inwhich many piezoelectric materials are used.

In an operating temperature range of an piezoelectric element, thepiezoelectric material according to the present invention is smaller intemperature dependency in piezoelectricity, higher in both density andmechanical quality factor, and satisfactory in piezoelectricity. Thepiezoelectric material according to the present invention does notcontain any lead component and therefore can reduce the environmentalload.

While the present invention has been described with reference toexamples, it is to be understood that the invention is not limited tothe disclosed examples. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2013-146304 filed Jul. 12, 2013 and No. 2014-109341 filed May 27, 2014,which are hereby incorporated by reference herein in their entirety.

What is claimed is:
 1. A piezoelectric material comprising: a maincomponent containing a perovskite-type metal oxide that can be expressedby the following general formula (1); a first subcomponent containingMn; a second subcomponent containing Li; and a third subcomponentcontaining Bi, wherein the content of Mn on a metal basis is not lessthan 0.04 parts by weight and is not greater than 0.36 parts by weightwhen the metal oxide is 100 parts by weight, the content α of Li on ametal basis is equal to or less than 0.0012 parts by weight (including 0parts by weight) when the metal oxide is 100 parts by weight, andcontent β of Bi on a metal basis is not less than 0.042 parts by weightand is not greater than 0.850 parts by weight when the metal oxide is100 parts by weight(Ba_(1-x)Ca_(x))_(a)(Ti_(1-y-z)Zr_(y)Sn_(z))O₃  (1) (in the formula (1),0.09≦x≦0.30, 0.025≦y≦0.085, 0≦z≦0.02, and 0.986≦a≦1.02).
 2. Thepiezoelectric material according to claim 1, wherein a relationship0.055<y<0.085 is satisfied with respect to “y” in the general formula(1).
 3. The piezoelectric material according to claim 1, wherein thepiezoelectric material includes a fourth subcomponent containing Mg, andthe content of the fourth subcomponent on a metal basis is equal to orless than 0.10 parts by weight (excluding 0 parts by weight) when theperovskite-type metal oxide that can be expressed using the generalformula (1) is 100 parts by weight.
 4. The piezoelectric materialaccording to claim 1, wherein the piezoelectric material includes afifth subcomponent that contains at least one of Si and B, and thecontent of the fifth subcomponent on a metal basis is not less than0.001 parts by weight and is not greater than 4.000 parts by weight whenthe perovskite-type metal oxide that can be expressed using the generalformula (1) is 100 parts by weight.
 5. The piezoelectric materialaccording to claim 1, wherein a relationship y+z≦(11x/14)−0.037 issatisfied in the general formula (1).
 6. The piezoelectric materialaccording to claim 1, wherein a relationship x≦0.17 is satisfied in thegeneral formula (1).
 7. The piezoelectric material according to claim 1,wherein the Curie temperature of the piezoelectric material is equal toor greater than 100° C.
 8. The piezoelectric material according to claim1, wherein a dielectric tangent of the piezoelectric material at afrequency of 1 kHz is equal to or less than 0.006.
 9. A piezoelectricelement that includes a first electrode, a piezoelectric materialportion, and a second electrode, wherein a piezoelectric material thatconstitutes the piezoelectric material portion is the piezoelectricmaterial according to claim
 1. 10. A multilayered piezoelectric elementthat includes a plurality of piezoelectric material layers and aplurality of electrode layers including at least one internal electrodethat are alternately multilayered, wherein the piezoelectric materiallayer is made of the piezoelectric material according to claim
 1. 11.The multilayered piezoelectric element according to claim 10, whereinthe internal electrode includes Ag and Pd and a relationship0.25≦M1/M2≦4.0 is satisfied with respect to a weight ratio M1/M2, inwhich M1 represents the content of Ag and M2 represents the content ofPd.
 12. The multilayered piezoelectric element according to claim 10,wherein the internal electrode contains at least one of Ni and Cu.
 13. Aliquid discharge head comprising: a liquid chamber that is equipped witha vibrating unit in which the piezoelectric element according to claim 9is disposed, and a discharge port that communicates with the liquidchamber.
 14. A liquid discharge apparatus comprising: a portion on whichan image transferred medium is placed, and the liquid discharge headaccording to claim
 13. 15. An ultrasonic motor comprising: a vibratingbody in which the piezoelectric element according to claim 9 isdisposed, and a moving body that contacts the vibrating body.
 16. Anoptical device comprising: a driving unit that includes the ultrasonicmotor according to claim
 15. 17. A vibrating apparatus comprising: avibrating body in which the piezoelectric element according to claim 9is disposed on a vibration plate.
 18. A dust removing apparatuscomprising: a vibrating unit in which the vibrating apparatus accordingto claim 17 is provided.
 19. An imaging apparatus that includes the dustremoving apparatus according to claim 18 and an image sensor unit,wherein a vibration plate of the dust removing apparatus is provided ona light-receiving surface of the image sensor unit.
 20. An electronicdevice in which a piezoelectric acoustic device including thepiezoelectric element according to claim 9 is disposed.
 21. A liquiddischarge head comprising: a liquid chamber that includes a vibrationunit in which the multilayered piezoelectric element according to claim10 is disposed, and a discharge port that communicates with the liquidchamber.
 22. A liquid discharge apparatus comprising: a portion on whichan image transferred medium is placed, and the liquid discharge headaccording to claim
 21. 23. An ultrasonic motor comprising: a vibratingbody in which the multilayered piezoelectric element according to claim10 is disposed, and a moving body that contacts the vibrating body. 24.An optical device comprising: a driving unit in which the ultrasonicmotor according to claim 23 is provided.
 25. A vibrating apparatuscomprising: a vibrating body in which the multilayered piezoelectricelement according to claim 10 is disposed on a vibration plate.
 26. Adust removing apparatus comprising: a vibration unit in which thevibrating apparatus according to claim 25 is provided.
 27. An imagingapparatus that includes the dust removing apparatus according to claim26 and an image sensor unit, wherein a vibration plate of the dustremoving apparatus is provided on a light-receiving surface of the imagesensor unit.
 28. An electronic device in which a piezoelectric acousticdevice including the multilayered piezoelectric element according toclaim 10 is disposed.